Tuesday, September 27, 2022

Climate Thread 1: Urgency - Emissions, Atmospheric Levels, Warming, Momentum, Feedback

Introduction

(Note: I have been updating this as I get more information. Latest update was 2024-04-09.) 

Climate change is the most serious and urgent problem we face. If (like most people) you don't agree with this, please bear with me as I explain. It is not possible to really understand this through memes or the type of reporting you get from the news media or from reading a few climate science studies. For years I've been posting articles and studies on Facebook, but it seemed to have very little effect. At one point I realized that facts and estimates, considered in isolation, are not what makes this so serious and urgent. It's only when you connect them together that you can begin to understand why it is necessary to work MUCH harder to turn things around, without delay. Even many climate scientists don't realize how serious and urgent it is, because they are focused on their own subset of the science. That's why I decided to write these climate threads, focusing on these types of connections. This first thread will focus on some basic, important parts of the science that can help explain the urgency side. 

You might react to this first thread by thinking or feeling like there is no hope, which is understandable. But please don't fall into the trap of believing that emotional reaction is the truth. It is true that we have delayed dealing with this for so long that now it will be much more difficult to fix it. But we still almost certainly have the ability to turn things around, if we work hard enough. But it may not take many more years of business as usual to make the problem unsolvable. Whether the situation truly becomes hopeless is up to us, the people alive right now. I plan to write another climate thread with some of the many solutions we can combine to turn things around, and I'll also touch on that subject a little in this thread. Just remember, it is not a hopeless situation yet.

You might also react to this thread by thinking it doesn't sound that catastrophic. This thread focuses on things like how hot the temperature could get. We all know that the hotter it gets, the worse things will get, but this thread doesn't go much into the effects of that heat. I plan to write another thread on that subject too. For now I'll just say that it is not at all certain that the human species will survive this. 

National Emissions

It is well known that we need to reduce greenhouse gas emissions to fix the climate problem. Most solutions center around things like solar and wind power, electric vehicles, and so on. But it’s important to keep in mind that what actually makes a difference is not how many solar panels and electric cars a country has, but how how quickly it reduces its greenhouse gas emissions. For example, China has about 75% more rooftop solar than the U.S. and more than 3 times as many electric cars, but its CO2 emissions levels are about double those of the U.S., and they are rising (while US CO2 emissions have generally been slowly falling since around 2007). This is because China has been rapidly expanding its manufacturing capacity and bringing electricity to more of its people. So at the same time that they deployed a lot of green energy, they also built a lot of coal fueled power plants, deployed more fossil-fueled vehicles, and so on. Until climate-friendly power sources lead to a reduction in fossil fuel emissions, they are only reducing our acceleration to self-destruction. And we are still accelerating, because globally, emissions are higher now than ever. This is also the fundamental shortcoming of the Inflation Reduction Act: it is almost all carrot and no stick.

By the way, if US corporations hadn’t moved most of their manufacturing to China and other countries, US emissions would be much higher, while China’s would not be as high. In addition, the US has recently become the world's largest producer of fossil fuels. Unfortunately, almost no countries have done anything close to what they should have done so far.

Global Emissions

It would take a lot of work and money (for example, getting solar on 40 million homes and reducing fossil fuel burning an equivalent amount), but what if the US managed to reduce CO2 emissions by 5%? Do you think the earth would begin to cool? One reason it wouldn’t is that global emissions, not local, drive global temperature change. And 5% of global emissions is a lot more than 5% of US emissions. To lower emissions globally by 5%, every country in the world would need to cut emissions by an average of 5%. But most countries intend to keep increasing their emissions for the next several years, or even decades, and many countries are too poor to do much to help. To decrease global emissions by 5%, relatively wealthy countries and the largest emitters would need to cut their emissions by a lot more than 5% and help poor countries to reduce their emissions.

Atmospheric CO2 Levels

What if the world managed to lower global emissions by 5% this year, would the earth begin to cool then? One reason it wouldn’t begin to cool yet is that atmospheric levels, not emissions levels, govern how much the earth warms. If this year the world emitted 95% of the CO2 it emitted last year, that would still increase atmospheric levels, just not as quickly. For this reason (and others given below), we would need to reduce emissions way more than 5% globally before the earth would begin to cool.

It would take a huge sustained effort, but what would happen if the world kept reducing global CO2 emissions by 5% per year for many years? A 2013 study by a team of scientists led by James Hansen calculated that if the world began reducing CO2 emissions 5% per year in 2020, atmospheric levels would peak around 2027 or 2028, then finally begin to slowly fall. They would fall to 400 ppm soon after 2050 but would not fall to 350 ppm until roughly 2300. Not 2100 or 2200, but 2300! If we waited until 2030 to begin reducing CO2 emissions 5% per year, atmospheric levels would peak around 2040 and wouldn't return to 400 ppm until around 2140. The chart from the paper (below) only goes to 2500, but it looks like atmospheric levels would not reach 350 ppm until roughly 2700. In other words, waiting 10 years would make the task take almost 400 years more! (Are you beginning to understand the urgency?)

If we begin reducing emissions by 5% per year in 2050, the peak level would be way too high, and it would take so long to get back to normal levels that it doesn't even make sense to consider this option, as you can see in chart below. Not understanding details like this made people think this problem was not that urgent and gave governments excuses to do little to solve it years ago, when it would have been much easier. Incredibly, most governments are still putting off making effective policies that would quickly cut CO2 emissions. (I extended the lines in the graph past the year 2500, so that part may be a little off. BAU means Business As Usual.)


Methane

When atmospheric CO2 levels do begin to fall, surely the world will begin to cool then, right? Unfortunately, not right away. For one thing, the above predictions only dealt with CO2 levels, and that is not the only greenhouse gas. Methane causes many times the warming that the same amount of CO2 does. The amount of methane we emit is much smaller, but atmospheric methane levels have been increasing since around 2007 (partly because of increased fracking and natural gas leaks, partly because of climate feedbacks). If methane levels continue to increase, this will counteract at least part of the cooling that would have been gained from CO2 reductions. We have to simultaneously cut methane emissions. And the same is true for all other greenhouse gas emissions. A December 2022 paper by Hansen and other scientists (link below the next graph) says that the forcing from all greenhouse gases in 2021 was equal to a doubling of 1750 CO2 levels, which would be about 556 ppm, so the other greenhouse gases had about the same effect as 140 ppm more CO2. (But there is another twist to methane that can help, which I'll explain below.)

Momentum / Inertia

A few years ago, even most mainstream environmental organizations seemed to think the climate problem was similar to air pollution, that climate effects happened soon after CO2 was released, and that soon after we reduced emissions, things would begin to get better. Most people still think this is true, but as you have seen, climate change is different. 

For example, scientists estimate that 30 - 50% of CO2 emissions are currently absorbed by the ocean. Without this, atmospheric levels and warming would have risen faster. The oceans have also been absorbing roughly 90% of the warming caused by greenhouse gases. This has greatly slowed the surface temperature rise the greenhouse gases in the atmosphere otherwise would have caused. (More about this in the feedback section.)

It also takes a long time for the full warming effect of greenhouse gas emissions to be realized. The graph on the left below shows an older and newer estimate of how long the world would keep getting hotter if CO2  levels suddenly doubled. The red line should be more accurate, because it uses higher resolutions and better understanding of some factors included in the model, based on better and longer-term measurements. Both predictions show that temperatures will keep rising for at least 2000 years after completely stopping CO2 emissions, but the more recent model predicts that the warming will be greater. And note that even after 5000 years, temperatures have fallen little, if at all. 


See http://www.columbia.edu/~jeh1/Documents/PipelinePaper.2022.12.22.pdf

Important point: The time scale at the bottom of the graphs above is logarithmic, so the tick marks are only 1 year apart at the far left, then 10 years apart, then 100 years, then 1000 years. If the tick marks were all equal, you would see temperature rising much faster in the beginning and gradually rising slower and slower.

If you look at evidence scientists gathered years ago from the past, the last time atmospheric CO2 levels were around 400 ppm, average global temperature was about 4 to 7 degrees C above the average from 1960 to 1990. (See the second graph in the Feedback section, below.) Since we are already at around 420 ppm, we know we will get a lot more warming unless atmospheric levels fall significantly.

The momentum and inertia are not necessarily equal in both directions. In the transitions between maximum and minimum ice coverage of the past few hundred thousand years, it has taken a long time for temperature to peak, and a much longer time for temperature to fall again. One reason is that it takes longer for sea ice and glaciers to form than to melt. (They gradually grow from accumulating snow but can melt quickly when temperature rises). We have recently increased CO2 levels much faster than has happened in the earth's history, due to our geoengineering experiment of releasing greenhouse gases to the atmosphere, and it would take tens of thousands of years for all of the excess CO2 to leave the atmosphere naturally (without new geoengineering). Fortunately, CO2 levels would fall most quickly at the beginning and gradually fall slower and slower.

Aerosols

If we cut global greenhouse gas emissions 5% per year beginning this year, would the earth begin to cool when atmospheric CO2 levels finally begin to fall, roughly around 2032? One reason they wouldn’t is that in addition to greenhouse gases, burning fossil fuels puts tiny particles (aerosols) in the air. This pollution causes a lot of sickness and death, but it also helps to cool things down. This is currently fortunate, because it reduces the warming and all the bad effects the warming causes. As we reduce fossil fuel burning, reduced CO2 levels will cool the earth, but reduced aerosol levels will heat the earth. How will this play out?

Until recently, how much aerosols were cooling the earth was not at all certain. We haven't been measuring it directly, despite decades of calls for this by Hansen and other scientists (although I heard we may finally launch a satellite that can do so in 2024). It's very difficult to estimate the effects of aerosols using models. An estimate I heard of total aerosol cooling a few years ago was between 0.6 and 1.0 degrees Celsius. If true, without aerosols, by September 2022 we would have had around 1.7 to 2.1 degrees of warming instead of around 1.2 degrees. Because the amount of cooling has been very uncertain, aerosol effects are not usually included in climate models, predictions, or policies. In an interview with NASA's Dr. Nadine Unger, she said that their models suggest the planet would be about 1 degree C hotter without aerosols, the high end of the earlier estimate. If true, we would have already been over 2 degrees of warming before 2022 if not for aerosols. See https://climate.nasa.gov/news/215/just-5-questions-aerosols/

In December 2022, James Hansen and a team of several other scientists released a draft of a paper titled Global Warming in the Pipeline (first link under the graph below - the second link is the final peer-reviewed paper). The conclusions in the paper were so significant that I had to update this thread. For example, it concluded that aerosols are probably currently cooling the earth roughly 1.5 degrees. This would mean that aerosol cooling was masking more than half of the warming that GHG levels would otherwise have been causing. The blue shaded area in the graph below shows aerosols cooling by roughly 1.5 degrees, compared to ECS (Equilibrium Climate Sensitivity) warming, but longer term ESS (Earth System Sensitivity) warming from current greenhouse gas levels would be much higher, and the same aerosol levels would probably cool that by about 2 degrees C. More on this below.


Original draft: https://www.columbia.edu/~jeh1/Documents/PipelinePaper.2022.12.22.pdf
Final, peer reviewed version: https://academic.oup.com/oocc/article/3/1/kgad008/7335889

Unlike CO2, aerosols released by burning fossil fuels (and wood, charcoal, etc.) do behave like air pollution, because that is what they are. They cool things as soon as they are released, and their levels fall pretty soon after emissions stop (most is gone within a couple of years). It takes much longer for the full effects of rising CO2 emissions to be felt, and it takes even longer for CO2 levels to completely fall after emissions stop (hundreds to thousands of years for most to leave the atmosphere). This leads to a very important and worrying conclusion. Once we significantly reduce our fossil fuel burning, even though both CO2 and aerosol emissions will fall roughly the same percent, atmospheric levels of aerosols will fall much quicker than CO2. Remember, it's atmospheric levels that determine warming or cooling and thus climate changes. So at first we will have much less cooling from aerosols and a little less warming from CO2, which means global temperatures will actually rise at first. Not taking aerosols into account in models predicting temperature rise and getting ECS so wrong made us think that things were not nearly as bad as they actually were and created the illusion that we had a lot more time than we did. This (along with pressure from the fossil fuel industry and others) helped lead to delayed and completely inadequate responses by almost all governments.

ECS and ESS

ECS is how much warming is expected in the shorter-term (maybe a hundred or so years) from a doubling of CO2 levels. (ECS includes some feedbacks, but not longer-term feedbacks, which ESS includes. More on this below.) For years ECS was thought to be between 1.5 and 4.5 degrees C, and many climate models were based on the midpoint of 3 degrees. Studies based on more recent knowledge have pointed to a narrower ECS range with a higher midpoint of 3.5 degrees. This paper concludes ECS is 3.6 - 6 degrees C, with a midpoint of 4.8 degrees C (or 1.2 degrees C per Watt per square meter, the red line in the graph above). Note that the low end of this range is higher than the midpoint of the traditional range. If this paper is correct, models have in general been greatly underestimating how hot a given atmospheric CO2 level would cause over 100 or so years. (Most models have not even attempted to predict beyond the year 2100.)

Feedback

Pre-industrial CO2 levels were around 280 ppm, so a doubling would be 560 ppm. You might be wondering why the more recent prediction in the graph in the "Momentum / Inertia" section only shows about 3.5 degrees of warming for doubling CO2 levels, when in the past, a level of only 400 ppm was associated with temperatures 4 to 7 degrees hotter. This is because (as mentioned above), the ECS that models have been using is 3.5 degrees, which is quite a bit too low, according Hansen. Another reason is that ECS doesn't take into account some of the warming feedbacks that will make the temperature rise further in the longer term.

Momentum and inertia can significantly slow down changes, and some of this is due to various feedbacks. But feedbacks can also speed up changes enormously. When I first started studying climate science, what worried me the most was feedbacks reaching their “tipping point”. This is what led in the past to huge changes in a short period of time. (Have you ever heard a sudden, very loud screech coming from an amplified microphone? That happens when a positive feedback in the sound system reaches its tipping point.)

In 2007 I realized that I had read over and over that one climate scientist or another had said that some aspect of climate change was worse than previously thought. That has continued to this day (some examples are above), and I still very rarely read that anything is better than previously thought. I wondered for a long time what could cause this. At this point I think it was caused by a combination of things. The IPCC reports seemed to base their predictions on models, and models are based on the formulas and values given to them. If you can’t give numbers to something you can’t include it in a model. For example, the first IPCC prediction I read for how much sea level might rise by 2100 was a few centimeters at the most. But I knew that paleo-climatologists had discovered that in the past sea level has risen several meters in a century or less, so I was confused that the IPCC prediction had such a small maximum number. Later I learned that their prediction was based solely on thermal expansion, or how much water expands when it heats up. Melting glaciers and ice sheets were not included in those early models because they didn’t have a good enough idea of how fast they were melting, much less how that would change with time. Obviously this would make the high end of their prediction (and the low end) way too small. There was also an enormous amount of pressure on the scientists from climate deniers, who would pounce on anything that they could criticize. Even though most of their criticism was garbage, I think it made the scientists think they had to be very cautious. If it turned out that they had overestimated a threat, the deniers would use that to attack them and sow doubt about the rest of their work. It was extremely important that people believe their work was valid. The result is that they greatly underestimated the threat and the urgency. 

In the "Momentum / Inertia" section I mentioned ways that the oceans slowed down warming by absorbing CO2 and about 90% of the excess heat caused by greenhouse gases. If atmospheric levels remained steady, the ocean would absorb less and less CO2 until equilibrium was reached. If all emissions stopped, a similar thing would happen, but atmospheric levels would be falling, so equilibrium would be reached sooner. The result of this and other processes means CO2 would fall most quickly at first, then slower and slower with time.

But it's not as simple as the higher the CO2 in the atmosphere the more the oceans absorb. As the world heats up, ocean circulation will slow, which would lower how much CO2 the ocean would absorb, and eventually it would stop. If ocean circulation stopped, the oceans would absorb very little CO2. (A paper the Hansen team is working on, "Sea Level Rise in the Pipeline", will give evidence ocean circulation could stop within decades.) If ocean circulation slowed, it would also absorb less heat, and it would absorb very little heat if the circulation stopped. Both of these would greatly accelerate the heating of the planet's surface on land, and the consequences that go with excess heat.

The "Global Warming in the Pipeline" paper points out that in the last few years global warming has been accelerating. They conclude this was mostly due to reduced aerosol emissions. Models didn't include or underestimated the cooling effects of aerosols. The models also don't include longer term positive feedbacks, because ECS doesn't include them. They don't usually project past the year 2100, so they thought longer term feedbacks could be ignored.  But "Sea Level Rise in the Pipeline" will also show that large amounts of sea level rise could come in the century time scale, instead of millennium, as models assume.

Scientists have known for decades that feedbacks and tipping points exist in the climate system. For example, the periodic changes to the earth’s orbit and spin are gradual and smooth, as are the changes in solar radiation caused by them. But the temperature and CO2 changes that result from the solar radiation "forcing" are much less smooth. Also, even though the solar radiation cycles go up about the same amount of time that they go down, it takes about 6 or 7 times as long for the earth to cool on the bumpy ride from an interglacial to a glacial period as it takes to warm from a glacial to an interglacial period. This is because of differences in cooling and warming momentum and feedbacks. During the cooling period, the earth keeps cooling long after the overall solar radiation forcing has started to increase. But at a certain point the radiation causes the warming feedbacks to hit a tipping point, and then they increase relatively dramatically, driving temperatures up much more quickly than they went down (starting just before the tan-shaded regions in the graph below). 


See https://www.ncei.noaa.gov/sites/default/files/2021-11/1%20Glacial-Interglacial%20Cycles-Final-OCT%202021.pdf

This has been the long-term climate cycle for about 2.6 million years, before humans began to burn fossil fuels or even wood. Atmospheric CO2 levels stayed in the range of roughly 180 to 300 ppm, and global average temperatures ranged from roughly 5 degrees Celsius below to 1 or 2 degrees above the 1960 to 1990 average. This was a longer-term stable period, where the levels change a fair amount but almost always stay inside a certain range. The low numbers happened during glacial periods, when much more of the planet was covered with ice, and the high numbers were during the warmer interglacial periods, like the one we have been in for about the last 11,500 years.

At the current point in the cycle, CO2 and temperature levels should be falling very slowly on average. But because of human activity, they have been quickly rising, especially CO2 levels. There was another relatively stable period, between roughly 5 and 11 million years ago, when CO2 levels were around 350 ppm and global temperatures were in the range of about 1 to 5 degrees above 1960 – 1990 levels. But we have pushed atmospheric CO2 to a level it hasn’t been in roughly 15 million years. 


See
https://earth.org/data_visualization/a-brief-history-of-co2/

There was one period in the past when CO2 levels hovered near where they are now, roughly 16 to 20 million years ago, when temperature was 4 to 7.5 degrees higher than 1960 – 1990 levels. Many things can change over millions of years that affect temperature, so we should not assume we could stabilize CO2 at this level. And even if we could, we would not want to. Now that we have experienced some of the effects of a little over 1 degree of temperature rise, I don’t think anyone wants to experience the effects of a temperature increase 4 to 7 times as large.

A paper from 9/9/2022 predicted when some tipping points might occur. Combining paleoclimate data, observations, and computer models, they identified 9 global “core” tipping elements and 7 regional “impact” tipping elements. They found that there is a small chance that even the then-current temperature could be hot enough to cause 4 or 5 of the tipping points to occur. See chart below, and https://www.science.org/doi/10.1126/science.abn7950

The study also concluded that the tipping points of 7 climate systems enter the likely to occur range between 1.5 and 2 degrees (the Paris climate agreement goal), with 3 more tipping points possible but not likely. Four of those tipping points (the complete collapse of low-latitude coral reefs, the collapse of the Greenland and West Antarctic ice sheets, and widespread abrupt permafrost thaw) begin the likely stage at 1.5 degrees. Any of those feedbacks would be devastating. But another tipping point is even scarier. If permafrost thaw happens at a large enough scale, it will be impossible to prevent global warming from rising out of control, because it will release huge amounts of CO2 and methane. We absolutely must prevent this from happening. In other words, if this paper is correct, the Paris goals are not strong enough. Even if we limit warming to the lowest side of those goals (1.5 degrees), we would be in the range where a huge positive feedback is likely. That is not a risk we should be willing to take.

At this point, the world is not even planning (much less on track) to limit warming to the high end of the Paris goals. Under current policies, we would reach around 2.7 degrees of warming (and that is without additional positive feedbacks and it assumes aerosol levels don't go down or at least would heat the world less if they did). Even at around 2.3 degrees of warming, abrupt permafrost thaw and 2 other tipping points become very likely, 4 others are likely, and 6 more are possible. 


The above graph is from this article, which is about the paper whose link I gave in the paragraph above it: https://www.carbonbrief.org/global-warming-above-1-5c-could-trigger-multiple-tipping-points/

There is enough CO2 and methane stored in permafrost alone to dwarf what humans have released since the industrial age began. The abstract above does not say how much they expect the abrupt permafrost thaw to release, but it could easily be enough to trigger more tipping points, including some other positive feedbacks that would heat the world even more. Even if this study is pretty far off, another recent study said that the Amazon is close to its tipping point. This could eventually add an additional 1 degree of warming, which would undoubtedly cause much more CO2 and methane to be released from melting permafrost. We absolutely must prevent this from happening too. See https://www.scientificamerican.com/article/amazon-rain-forest-nears-dangerous-tipping-point/

The "Global Warming in the Pipeline" paper says that ECS (Equilibrium Climate Sensitivity) that includes shorter term feedbacks would cause about 4.8 degrees of warming for a doubling of atmospheric levels from preindustrial levels. However, this does not take some of the warming feedbacks into account. They also looked at the current best paleoclimate data, which includes all feedbacks, known and unknown, to come up with a CSS (Climate System Sensitivity) value. The graph below, from that paper, shows that current greenhouse gas levels, which are already roughly equal to a doubling of CO2, could cause about 10 degrees C of warming if there were no aerosols, once all the feedbacks and interactions reached equilibrium (green line). The world would would be completely different at that temperature.


This means that if we lowered emissions enough to keep greenhouse gas and aerosol levels where they are now, it would eventually get almost 6 degrees hotter. And if we continued to reduce aerosol levels as we have been recently (by reducing pollution and switching from coal to gas electric power generation), it would get even hotter than that. Either way, all of the feedbacks from the other study mentioned above are pretty much certain to hit their tipping points before things got that hot. Some have the potential to release way more greenhouse gas than humans have in their entire history. I don't think anyone yet knows how much would actually be released or how quickly, but I think that in order to keep greenhouse gas levels constant, we would have to somehow remove huge amounts of greenhouse gases from the atmosphere for a very long time.

Net Zero

The Paris Agreements called for striving to keep global warming below 1.5 degrees C and definitely below 2 degrees C. The highest aspirations that most countries have made so far is to eventually achieve net zero carbon emissions. This does not mean zero emissions. "Net" means they plan to keep emitting as much as they remove from the atmosphere. Most countries are including natural carbon sinks in this equation. For example, if they have forests, they plan to be able to keep emitting as much CO2 as those forests absorb. Most are also counting on man-made ways of removing huge amounts of CO2 from the atmosphere so that they burn even more fossil fuels. Most people probably think that if all countries met their promises, greenhouse gas levels would soon go way down, and climate change then go away. Unfortunately, that is far from the truth.

Even if net zero could stop the warming, most countries are not even hoping (much less trying) to reach net zero before the year 2050. The current largest emitter (China) is even planning to keep increasing emissions until 2060, and only then begin lowering them. I doubt it could reach net zero until many years after that. The second largest emitter, the U.S., does aspire to reach net zero by 2050. It may or may not reach this goal, depending on who wins future elections to national office, priorities of voters, the economy, and other things. India, the third largest emitter, doesn't aspire to reach net zero until 2070. Russia, the fourth largest emitter, does not currently have plans to reduce emissions, so their emissions will probably keep increasing.

According to https://www.un.org/en/climatechange/net-zero-coalition, current goals would cause 11% more emissions than 2010 levels by 2030, but to achieve net zero by 2050 the world would need to have 45% less emissions by 2030. There is a huge gap between even this inadequate net zero and what countries are hoping to achieve.

From what I said earlier, the current large imbalance between atmospheric CO2 levels and temperature would eventually cause temperature to keep rising to approximately 3 degrees of warming, even before feedbacks kicked in. That would very likely trigger multiple warming feedbacks, including the abrupt permafrost thaw that would release much more CO2 and methane. The additional greenhouse gases would heat the earth's surface even more, which could trigger more feedbacks, releasing more greenhouse gases, and so on. Where would it stop? By using the most recent paleoclimate data to calculate earth's energy imbalance, the December 2022 paper I mentioned above (http://www.columbia.edu/~jeh1/Documents/PipelinePaper.2022.12.22.pdf) estimated temperatures would eventually rise to about 10 degrees C of warming. Ten degrees! I haven't even heard any predictions of what would happen if the world got that hot, but predictions for 6 degrees of warming are already unimaginable.

We would need to remove huge quantities of CO2 and methane from the atmosphere indefinitely just to keep atmospheric levels where they are. But we don’t have a proven method that can do this at a large enough scale. Even if we did, it would take a huge amount of energy, money, and other resources to implement. The energy can’t come from burning fossil fuels, because that would do more harm than good. But it will be extremely difficult just to generate enough non-fossil fuel energy for our other needs. Even if we did find a way to generate that much energy indefinitely, all that would still be in vain because temperature would eventually rise high enough to make even stronger feedbacks inevitable. It would be impossible to reduce atmospheric CO2 and methane enough, and quickly enough, to prevent any tipping point from happening, because reduced aerosols would raise temperatures, causing more CO2 and methane to be released. That means that now we have to find ways to quickly remove massive amounts of CO2 from the atmosphere and/or ways to cool the entire surface of the earth.

Conclusion

I hope it is clear now that this is our most urgent problem. In a later post, I will try to explain why it is also our most serious problem. But if you take my word for it for now, I think you'll agree that our main goal must be to reduce atmospheric greenhouse gas levels to a stable and much lower level. That means at least to 350 ppm, and maybe even 300 ppm or lower, if 350 ppm is no longer relatively stable like it was more than a million years ago. We have to do this before we hit tipping points of any warming feedbacks, which get more likely each fraction of a degree the earth warms. That means we can’t delay. Much stronger measures than governments are talking about must be taken very soon. 

We need to completely stop burning all fossil fuels as quickly as possible. There is simply no way around this. If we don't do this, we will fail. However, it should be obvious from the above that stopping all burning of fossil fuels is no longer enough. The effects of quickly falling aerosol levels will be much stronger than the effects of slowly falling CO2 levels and could easily cause multiple climate tipping points, including some that might release more greenhouse gases than humans ever have. This would be runaway global warming that would quickly go beyond our control or even our ability to survive and would cause a huge mass extinction. We can't accept that. So what else can we do?

Reducing methane emissions would help (and fortunately, this is being discussed by some elected leaders). It takes around 9 years for about half of the methane released to leave the atmosphere, much less than CO2. Unfortunately, much of that methane leaves the atmosphere by turning into CO2 and water. But methane is such a strong greenhouse gas that even after 20 years, with 11 of those years (on average) as a CO2 molecule, it still warms the earth about 85 times as much as the same amount of CO2 would over the first 20 years. Since methane is not released from burning fossil fuels, reducing methane emissions won't reduce aerosol levels. This means that reducing methane emissions at the same time as we reduce fossil fuel burning would cause less warming, especially during the first few years. We need to detect and stop methane leaks, quickly change food production methods to reduce their methane emissions, do the same for waste systems (landfills, etc.), and so on. According to the IAEA, methane causes about 30% of our current warming (see https://www.iea.org/reports/global-methane-tracker-2022/methane-and-climate-change ). And we know we won't be able to stop all methane leaks as long as we keep producing fossil fuels. At the rate global heating is going now, it would probably only take a couple of decades to erase that benefit.

But we should not fool ourselves or let ourselves be fooled. If we reduce methane levels without significantly reducing the burning of fossil fuels, it will make temperature rise slow down, maybe even stop or go down slightly if we did it quickly enough. Many people would inevitably think we had solved the problem and made great progress, when in reality we would have only slightly delayed the crises. Politicians and fossil fuel companies would congratulate themselves on their accomplishment, but once the easy and relatively cheap methane reductions had been accomplished, global heating would happen faster than ever. And our job would be even more difficult and urgent than it is now. Unfortunately, that seems to be what leaders are thinking of doing. At the 2023 COP, leaders and oil companies agreed to reduce methane emissions, and they did call for a transition away from fossil fuels, but there is no timeline, no commitment, and no means of enforcement or any type of penalty for not doing so.

We also need to completely halt the destruction of all natural carbon sinks (forests, and so on). This must happen extremely quickly. We also need to work hard to restore natural carbon sinks that we have been destroying, so they can remove more CO2 from the atmosphere. It will take time for restoration like this to have much effect, and this is essential for a long term solution. But even adding that to drastically cutting methane emissions would not be enough in the short term.

We need to find other ways to cool the earth and to remove CO2 from the atmosphere, until atmospheric CO2 levels fall enough to take us out of the danger zone. I don't know of any way to do this other than geoengineering. Geoengineering is a broad term that even includes burning fossil fuels (although we haven't been doing this with the goal of heating the planet). There have been efforts to remove CO2 from the atmosphere via technology for a few years, but so far they have had hardly any effect. A new study says that we currently release about 37 billion tons of CO2 per year and only about 2 billion of those are re-absorbed. Only a tenth of a percent of that 2 billion were removed by these artificial means. To get a visual sense of this, I created this graph. The amount removed by artificial means (geoengineering) is so small in comparison, I can barely see it. This shows how far we need to go before this method will make much difference. 




See https://apnews.com/article/science-europe-climate-and-environment-forests-bd31a9206e67c47bdc5296f68841b394

We need intensive government funded programs to research and then implement the safest, cheapest, and most effective geoengineering method(s) to cool the earth. Because of the risks, I used to think we should research, but not implement geoengineering except as a last resort. But we need to admit that we probably can no longer avoid it. Fortunately, there are some promising ideas that seem like they might not have very bad side effects, or that could be quickly halted if they do. Unfortunately, we haven't done much research yet.

We should also fund more climate research and tools like satellites to measure things that we need to know about, such as the current levels of emissions from climate feedback systems like melting permafrost and measurements of cooling from aerosols. The more details we know, the better we will know what steps to take.

We need to find and adopt better and cheaper ways to replace what burning fossil fuels currently provides (energy, industry, transportation, and so on). Although this is not required to solve the climate problem, it is necessary for us to maintain or improve our standard of living. Cheap energy storage is a huge need, along with more advanced electric transmission systems to take electricity where it is needed.

All this will take huge amounts of work, money, resources, time, political will, and pressure from the people to create the political will. Only if people are aware of our situation will they be willing to do all this. People don’t like to hear bad news and have a hard time accepting it. But the first steps to solving any problem are becoming aware of it and accepting it. We can’t run away from this problem, and we can’t wish or pray it away. We have to willingly face it, accept it, and work like hell to solve it. If we don’t, we will be forced to face the consequences. We already face effects ranging from damages and deaths caused by worsening disasters to hunger, famine, migrations, and conflicts caused by long term droughts and other changes. But it will get unimaginably worse if we fail to stop it. Humans won't be able to physically survive in many locations, the plants and animals we depend on won't be able to survive. I think a huge mass extinction would be inevitable, including humans.

This first climate thread may have made you feel like the situation is hopeless. It's good to feel whatever emotions you feel - anger, despair, sadness, or whatever else. But please remember that those are your emotions, not truth or reality. But instead of wallowing in those feelings, use them to motivate you to start taking actions now, and continue until we cool the planet sufficiently. There are many things you can do, from the personal level to the global level. But the biggest deficiency is the lack of action at the international and national levels to reduce greenhouse gas emissions and take CO2 out of the atmosphere. Only such action at a huge scale can save us now. Only national and international governments have the power to make massive changes quickly. So let leaders and politicians know every chance you get that their policies and actions related to this issue are by far the biggest reason why you will or won't support them. And follow through on that with actions. That is the most important thing you can do. You may not believe there is any way we can solve this problem, but humans have done unbelievable things in the past, things that nobody thought was possible. We can do it again, and we must.

Thursday, June 12, 2014

Taking Climate Change Seriously


Global warming is the world’s most serious and urgent threat, and stopping it must become our top priority. If you think that any other issue is more important or urgent, please keep reading. The urgency and danger aren’t separate, but I will alternate my focus between them and try to put this issue into perspective. 

Urgency: A few years ago, most nations agreed that we need to limit warming to 2 degrees C above late-1800 levels. But there is strong evidence that is much too high. I will show why later, but for now, assume that we should try to limit warming to about 1 degree. James Hansen and an international team of scientists came out with a paper in December 2013 that shows what it might take.1

The charts below are from page 8 of this paper. Currently CO2 emissions are rising about 2% per year, and you can see how steeply the level of CO2 in the atmosphere is rising. The charts show how CO2 levels would change if we reduced emissions beginning in 2013 (left chart) or later (right chart).


We need to get CO2 levels below the horizontal dotted line (350 ppm). The longer they are above that level, and the higher the peak lever, the riskier our situation becomes. Notice how much longer it takes if we wait before reducing emissions, or if we reduce them by a smaller amount. If we start immediately and reduce worldwide emissions by 6% per year, we would be under the dotted line in around 100 years. If we wait until 2020 and reduce by 5% per year, it would take about 300 years to get CO2 to safe levels. A 7 year delay and 17%  smaller reduction level triples the amount of time it takes! On the other hand, if we had begun in 2005, a 3.5% reduction per year would have brought us to safe levels by 2100. If we had started only 15 years earlier, 40% smaller reductions would have gotten us there in 200 years less time! (See p. 10 of the Hansen paper for more details.) This why the problem is so urgent. Any delay is extremely foolish, because it makes the job much more difficult and makes our future much more dangerous.
This paper assumes that in addition to reducing emissions, we will store 100 GtC (gigatons of carbon) in plants and the soil by 2100. That means stopping deforestation, reforesting much of the land we have deforested, and implementing farming techniques that put carbon into the soil. If we only put 50 GtC back, we would have to reduce emissions by 9% per year beginning now in order to get to safe levels by 2100. (The paper didn’t state this, but I suppose that if we don’t put any carbon back in the ground, reductions would have to be roughly 12% per year.)
The paper also assumes that we will simultaneously reduce methane and other greenhouse gases in order to counteract the reduction in particles that have a cooling effect (which will be reduced as we burn less fossil fuel). Doing all this will be a huge task, but to not do it would be insane.
Danger: As I will show below, harmful effects multiply quickly as temperature rises more than 1 degree. But even keeping the warming to 1 degree would not save us from all the bad consequences. With only 0.8 degrees of warming so far, we are already seeing many effects2, including these:
·         Increased weather extremes (droughts, storms, fires, etc.) have caused property damage, loss of life and crops, higher food prices, and economic damage.
·         Increased destruction of forests by fire and pests has caused economic and ecosystem damage.
·         Diseases have spread to new locations.
·         Sea level rise has caused erosion of coastlines and worse flooding.
·         Melting permafrost has caused damage to buildings and infrastructure.
·         Bleaching and die-off of corals has increased dramatically.
·         Rising ocean acidity has begun to threaten some species and harmed shellfish industries.
·         The already very high extinction rate has increased.
·         Some areas have experienced water shortages caused by shrinking glaciers and snowpack.
·         Expanding deserts and rising food costs have caused or exacerbated conflicts and unrest.
·         Feedbacks with huge potential have already started happening. (Melting permafrost and thawing methane hydrates on ocean floors release more greenhouse gases.)

The effects of warming do not all come immediately. Feedbacks can take decades or more to have their full effect. About 90% of the extra heat has warmed the oceans, and it takes roughly 1,000 years for water to complete the full ocean journey along the global conveyor belt3, so it will be a long time before the warming is fully distributed. Even if surface air temperatures remained where they are now:

·         Arctic sea ice would continue to melt, eventually making the Arctic Ocean ice-free for part of the year.
·         Glaciers would continue to melt, and many of them would disappear.
·         Greenland and Antarctic ice sheets would continue to melt (and sea levels rise), for decades to centuries.
·         As ocean floors gradually warm, more methane will be released, causing more warming.

But surface temperatures won’t remain where they are unless we dramatically lower atmospheric levels of greenhouse gases. We have probably seen less than half the warming that current CO2 levels would eventually cause, even without feedbacks that cause greenhouse gas levels to rise further. Temperatures will go up for even longer, because of the huge momentum of the climate system. And as the last bullet point above indicates, feedbacks will take CO2 and methane levels even higher. Besides the things above getting worse, predictions for only a little more warming include these:

·         Sea level will rise high enough to flood many lower elevation islands and coastal areas
·         Areas experiencing droughts will increase, possibly by a factor of ten
·         Melting glaciers will cause floods and later droughts for millions of people and their crops
·         Droughts that last up to 5-6 decades each could occur in the U.S. Southwest
·         The Great Plains could turn into a desert

You might think that you would be fine as long as you didn’t live in one of the affected areas, but these things will have wide repercussions. Several of the above items would cause severe local food shortages, and because our food supply is increasingly globalized, they will affect food prices all over the world. There are already millions of hungry or malnourished people. Many more are just getting by. Higher food prices plus a shortage of food will mean millions more in hunger and poverty. Farmers in affected areas will lose their means of livelihood, as will those whose livelihoods are closely connected to those farmers. Worse disasters will cause more climate refugees, who won’t be able to buy products either. Most people will have to cut back on non-essential spending because of high food prices. That will mean layoffs and businesses closing in non-food industries too. This is guaranteed to have a negative effect on local economies and the global economy. Governments will strain to take care of growing numbers of people in need at the same time as tax revenues are falling.

Although the last two items in the list above are not certain to happen with 1 degree of warming, they both happened only a few hundred years ago, during the Medieval Warm Period (MWP), when global temperatures were probably slightly cooler than now. A paper by NOAA published in Science in 2004 concluded that the drought in the Western US at that time was similar to, but not as severe as the MWP droughts between 900 and 1300. It also predicted that droughts would intensify with more warming. A 2011 paper said the same area suffered much worse droughts in previous inter-glacials, when global temperatures were hotter. Some of these droughts lasted for over a thousand years.4 In other words, the hotter it gets, the more likely devastating droughts in this area become.

To delve a little deeper into these last two effects, think about what would happen if mega-droughts hit the U.S. Southwest. California, which currently grows roughly half of the country’s vegetables, nuts, and fruits5, would no longer be able to grow this food. Its economy (one of the largest in the world if it were a country) would be devastated, which would affect the U.S. and world economies. It would also cause the U.S. to rely heavily on imported food, which would cause food prices to rise worldwide. People would have to move out of California for economic and other reasons. Now imagine what would happen if, on top of that, the Great Plains turned into a desert. Instead of exporting grains and meat, we would have to import these too. The national and global economic consequences would be extremely bad. And this would not be a temporary crisis like the 2008 recession, because effects like these would last at least decades, probably centuries. Many other predicted effects would also reduce the food supply, and the combination of several of them would be catastrophic.

Perspective: Governments need to deal with many complex problems and prioritize issues based on many factors. The Obama administration’s “all of the above” energy strategy shows that short term “energy security” was seen as more important than stopping global warming. That makes no sense when you know what global warming could bring even with much more aggressive, worldwide emissions reductions than governments are considering. Green energy would give us both short and long term energy security, so it makes no sense at all to drill more oil, mine more coal, or refine more tar sands oil. The reasoning may have been that fossil fuels are cheaper, but they are cheaper only because we don’t include even the costs of their immediate adverse effects (including over a million deaths per year from pollution), much less the future effects of climate change.

Urgency 2: For years scientists have estimated that a doubling of CO2 would eventually cause global temperatures to rise 1.5 – 5 degrees C. This is the “climate sensitivity” of this gas. The paper above assumes CO2 sensitivity is 3 degrees C, near the center of this range. But a newer paper5 concluded that the possible sensitivity range is really 3 – 5 degrees. This would put the center of the range at 4 degrees, and that would move the dotted line to 330 ppm. If sensitivity turns out to be 5 degrees, then we would need to get CO2 levels below 318 ppm.

I added two more dotted lines to the charts below for these two sensitivities. I also extended the timeline a few hundred years on the chart on the right. You can see that if sensitivity is 4 degrees, the blue line would get us to safe atmospheric CO2 levels roughly 800 years from now instead of 300. And if sensitivity is 5 degrees, it will be hundreds of years beyond that before we are in the safe zone.


If sensitivity is 3 degrees, then 450 ppm would eventually bring us to 2 degrees of warming. But if sensitivity is 4 degrees, it would only take 405 ppm, and if it’s 5 degrees, it would only take 378 ppm. If we follow the blue line, we will be higher than 405 ppm for about 50 years and higher than 378 ppm for about 150 years. Even the solid black line on the left would keep us above 378 ppm for decades. In other words, we are probably already in very dangerous territory, and are definitely taking huge risks.

Danger 2: The effects of 2 degrees of warming are much more than twice as bad as the effects of 1 degree. Not only do the effects listed above get much worse, new effects will appear, including the following. (When I say “will”, assume that means “probably will”. Nothing is certain, but most of these will probably happen.):

·         The permafrost boundary will move hundreds of miles north, releasing CO2 and methane as it melts.
·         We will lose the majority of coral reefs and species that depend on them.
·         The oceans will be too acidic for the formation of some shells, imperiling shellfish, plankton, and the many species that depend on them.
·         The average summer will be hotter than 2003, when a heat wave killed tens of thousands of Europeans.
·         In China, shifting monsoons will bring widespread drought and food shortages.
·         India will see decreases in wheat and rice production and large scale die-offs of forests.
·         Food shortages will be common and food prices will soar in lean years.
·         Widespread conflicts seem very likely.
·         Flooding and fires will increase in many parts of the world.
·         Greenland will eventually lose much of its ice, forcing as much as half of humanity to move to higher ground.
·         The earth’s largest carbon source, the oceans, may absorb much less CO2, and a plankton die-off would also cause much less CO2 to be sequestered.

Perspective 2: If Obama had made dealing with climate change his top priority, he probably could have gotten something passed during his first 2 years. It may have been as imperfect as the health insurance reform he chose to focus on, but it would have been a beginning. Thousands were suffering and dying each year in the U.S. from lack of health insurance, so it was an urgent problem. But thousands are already dying each year worldwide from climate change. And unless you ignore the future, stopping global warming is much more important. When some of the effects above begin, deaths caused by climate changes will far outnumber the lives saved by the Affordable Care Act. In fact, the good done by the ACA will be fleeting if we don’t stop global warming soon enough. Think about what will happen when the huge negative economic effects happen. People who lose their jobs will need government assistance to pay their health insurance. But how will the government pay when tax revenue has fallen sharply? The answer is they won’t. There will be many more people without health care than before the ACA. And this won’t be a temporary setback. The climate will take at least hundreds to thousands of years to get back to normal. If Obama and other U.S. leaders had put things into perspective, they would have tackled climate change first.

Urgency 3: The Hansen paper talks about “slow feedbacks”, which might better be called “delayed” feedbacks. They are called “slow” because they don’t begin right away. But once they get going they can grow huge quickly. These large feedbacks are not included in climate sensitivity estimates. That means they are also not included in the chart above. Virtually all the predictions pretend like they don’t exist. Models don’t take them into account. But they do exist. The paper says that they probably won’t occur with 1 degree of warming but probably will with 2 degrees, and when they do occur, they will probably cause global temperature to rise an additional 1 to 2 degrees. This makes it even more important to keep global warming to 1 degree, because 2 degrees will probably become 3 to 4 degrees.

These feedbacks have already begun, but hopefully on a small scale. I say “hopefully” because we don’t yet have enough data to know how quickly they are growing. Melting permafrost that releases CO2 and methane is one of these feedbacks. Another is the melting of methane hydrates in shallow ocean waters. A few years ago scientists predicted that with 3 - 4 degrees of warming, the Amazon would begin to release carbon instead of absorbing it, as it turned into a savannah. A study came out a couple of years ago saying that although the Amazon rainforest used to absorb on average about as much CO2 as the US released each  year, in the 10 year period before the report came out, it released as much as it absorbed. This was due to two large droughts. This makes it look like the Amazon could become a source of carbon instead of a sink sooner than predicted. Whenever it happens, it would raise global temperatures by about 1 degree more. If all that isn’t enough, another recent paper6 concluded that if warming reaches 4 degrees, the “vegetation carbon sink” would end. That means plants will no longer remove CO2 from the atmosphere. This would make the CO2 levels stay high for a much longer time, especially with oceans absorbing less CO2 (which is also predicted to happen). If we let things go this far, the effects would probably last many thousands of years.

Danger 3: Since 2 degrees of warming is likely to turn into 3 - 4 degrees even with no additional human emissions, you should assume at least some of the following predictions could be listed under 2 degrees. In addition to previously listed effects becoming stronger:

·         Snow caps in the Alps will all but disappear.
·         Heat waves like those in the summer of 2003 will become the norm.
·         Monsoons will become more variable, flooding more or raining less.
·         There will be perennial drought and famine in much of southern Africa. Botswana may be entirely covered by shifting sand dunes.
·         The Indus, which is practically the only source of water for Pakistan and part of India, will be dry for months of the year. Other rivers fed by Himalayan glaciers and supplying water to millions in China, India, and other countries will produce much less water.
·         New York City will have 100 year floods every few years.
·         New Orleans and other low elevation coastal areas will have to be abandoned.
·         Yields of rice, wheat, and corn will decline in temperate and especially tropic regions.

Perspective 3: Many people think that hunger and poverty are more urgent and serious issues than global warming. But how much worse would hunger and poverty be if global food production was reduced by 25%? A recent paper7 predicted that decreases of 25% would be increasingly common by the second half of this century. Population is predicted to rise by more than 35% by 20508. That means periods with about 45% less food per person by mid-century. These two things alone will dramatically increase both hunger and poverty. In fact, famine will be inevitable in most parts of the world. Of course we should deal with hunger, poverty, and all the other important issues we currently face. But if we don’t stop global warming soon enough, all the other good we do will be temporary, and the situation will be worse than ever.

You can do a similar exercise with whatever issue you think is more important than climate change. I already showed how healthcare and the economy would be severely negatively affected. For another example, violence and unrest will increase dramatically when people are hungry and there are millions of climate refugees. So if security is important to you, you should be trying to stop global warming. If preventing and curing sickness and injury is important to you, you should know that climate change has been called the biggest health threat we face. Among the reasons are that the number of deaths from heat waves will rise dramatically, deaths directly caused by other extreme weather events will go  up, climate refugee camps will be breeding grounds for diseases, tropical diseases will spread to more areas, and people who are malnourished or starving get sick much easier.

I hope you understand now why I said at the beginning that we need to try to keep warming below 1 degree. Fortunately, it takes a while for temperature to catch up with rising CO2 levels. So if we lower emissions quickly enough, temperatures won’t go as high as the peak CO2 level indicates. On the flip side, there is a lot of inertia to the warming, so surface temperatures will continue to rise for years or decades after CO2 levels begin to fall (depending largely on how quickly we reduce emissions). By not taking this problem seriously up to now, we have committed ourselves to living with increasing chances of triggering strong feedbacks and suffering the consequences. Some effects will definitely continue to worsen for a long time after CO2 levels fall. For example, sea level may continue to rise for centuries no matter what we do. This is what makes it our most urgent problem. We probably still have time to avoid the worst consequences, but only if act quickly and aggressively.

Urgency 4: Seeing how slow the world has been so reluctant to tackle this threat, I am worried that it may take a huge disaster to wake enough people up, and that by then it will be too late. What do I mean by that? Some people are already saying it is “too late”, but too late for what? It is probably too late to prevent sea levels from rising at least a few more inches, to prevent global temperature from rising more before it can begin to fall, to prevent the Arctic seas from being ice free for part of the year, to prevent more severe weather events than we already see, or to prevent the extinction of some more species. There is so much momentum in the system that many things like this will get worse before they get better. But it is probably not too late to prevent most of the effects I’ve listed above. For example, ocean acidity will begin to fall soon after atmospheric CO2 levels fall. If we prevent the large feedbacks from growing too strong, we can bring CO2 levels down.

The large feedbacks did not kick in too strongly during the hottest part of the current warm interglacial, so that is a good sign that they will probably not kick in if we keep warming below 1 degree C. If sensitivity is 5 degrees, 324 ppm is enough to warm the earth that much. So the safest course would be to get the CO2 level that low before temperature catches up with it. From the charts above, you can see that reductions of 5 or 6% per year are not large enough – it would take many hundreds of years to get back to 324 ppm. Even if sensitivity is 4 degrees, we’d need to lower CO2 levels to 338 ppm, which would take a couple hundred years if we begin 6% reductions now. Therefore, we really should make even larger reductions, at least at first. I would say 10% per year should be our minimum target if we start right now (and the target should rise every year that we don’t meet the target). It’s possible we would be safe if we made less than 10% reductions, but knowing the risks, would you really want to take that chance? If we were reasonable, we wouldn’t.

But so far we have not been reasonable at all. Few are even willing to discuss reducing emissions this much. They think large emissions cuts would be “too painful”. But compared to the pain the alternative will bring, the pain of cutting emissions is nothing. People who complain about the pain of making cuts should have demanded we start cutting emissions a few years ago, when the cuts per year could have been much smaller. Focusing on the pain of making cuts only promotes delay and makes the necessary cuts higher still. It is another form of denial. If we wait for a huge disaster that forces everyone to face reality, climate momentum will ensure that much larger disasters will follow. Dealing with the effects of disasters always comes before efforts to prevent another disaster, and reacting to a very large disaster will take a huge amount of resources. The numbers of small and medium disasters will already have been increasing, with more and more resources needed to deal with their effects. Each of these will do some damage to the economy, and when severe food shortages hit, that will completely devastate the global economy. (In fact, famine could very well be the big disaster that finally wakes us up.) Remember that the longer we wait the higher the emissions reductions will need to be. As the job gets tougher, our abilities will weaken. I don’t see any way we could have the resources to make such changes. Famine would be followed by mass extinction. We will be locked in a downward spiral of worse disasters and less ability to deal with them, while feedbacks make greenhouse gas levels higher than ever. The suffering and death in such a world is difficult to imagine. But if you try to imagine it, you will understand what I mean when I say “too late”.

Danger 4: I’ll end with what I think is the most serious danger. Extinction rates in modern times have been many times higher than normal because of human activities other than greenhouse gas emissions (over-fishing, over-hunting, deforestation, the spread of invasive species, pollution, etc.). Climate change has already added to the extinction rate and will add dramatically more if we don’t work very hard to prevent it. Below are extinction predictions from the 2007 IPCC report9.

·         1.2 – 2.0 degrees of warming:  9-31% (mean 18%) of species committed to extinction
·         2.1 – 2.3 degrees of warming: 15-37% (mean 24%) of species committed to extinction
·         2.6 – 3.3 degrees of warming: 21-52% (mean 35%) of species committed to extinction

If we continue as we have been, warming will go way beyond 3.3 degrees. That could cause over half of species to die off, qualifying as the sixth great extinction in the history of earth. Even reducing emissions with a target of 2 degrees of warming could lead to 3 - 4 degrees of warming when feedbacks happen, and that could be enough to cause a mass extinction. It is very difficult to predict extinction rates. Many people would think the rates above are unbelievably high, but I think they could easily be too low. Usually scientists who make such predictions don’t factor in things like what will happen when there are huge numbers of desperate, hungry people. Most people who are starving would care more about eating than about saving endangered species. Over-fishing and over-hunting and deforestation would go into overdrive. That would make a mass extinction much more likely.

Do we really want this to be our legacy? Do we want to be the species that caused a mass extinction? I know some people will try to whitewash this with thoughts such as, “Life will go on.” If everything but single-celled organisms died off, life would go on. But not the life we care about, not the life we depend on for our survival, and not us. Many people think we are so far above all the other forms of life that we could survive a mass extinction. But they don’t realize how completely we depend on other species, how almost all species depend directly or indirectly on many others. Even if our species survived, there would be very few of us left. I have no doubt that all our systems and civilization itself would collapse. I don’t think most people realize that when a mass extinction happens, it’s not just that many species go extinct. Most of the species that survive are greatly reduced in numbers for a long time (except for a short spike in species that live on decaying matter). Worst of all, in the past it has taken millions of years for biodiversity to recover from such an event. Species can die off quickly, but new species evolve very slowly. Each species we cause to go extinct is a terrible tragedy. Causing a mass extinction is the worst possible thing we could do. But unless we all work hard to make the necessary changes quickly, a mass extinction will be our legacy.

Perspective 4: You might think there is no way we can make the necessary changes to our energy and transportation systems quickly enough. But I know we can, because we have made huge changes extremely quickly in the past. Less than three months after Japan attacked Pearl Harbor, the huge U.S. auto industry completely stopped making cars and trucks for domestic use and began making tanks, jeeps, trucks, airplanes, and other equipment for the war effort. That is a huge change in an incredibly short period of time. Other industries were also transformed very quickly at the same time. In just months, we were churning out huge numbers of ships, planes, tanks, and weapons. Huge research efforts were begun, including the one that led to the atomic bomb. Practically everyone pitched in. We did it because we knew we had to. If we had lost the war, our country would have been changed drastically, by force. Freedom and Democracy would have been lost. The world would have been a very different place.

Now we face a much greater danger. Losing the war would have been terrible, but most of us would have survived, and eventually we could have won back whatever freedoms and rights we had lost. With global warming, our entire civilization, maybe even our species, is at risk.

Reducing emissions by 10% each year is a huge task, but it is not impossible, not yet anyway. What will be impossible is preventing massive suffering and death if we don’t begin making large reductions very soon. Each year we delay is sentencing countless innocent people and other forms of life to death. If you value life at all, you must make stopping global warming your top priority, and you must demand your government do the same.

2.       Current effects are compiled from various studies and news reports. Most predictions are from “Six Degrees” by Mark Lynas and the IPCC reports.
4.       “Climate Change – Biological and Human Aspects, Second Edition” by Jonathan Cowie, p. 308