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 behaved as if they thought 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
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.
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
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).
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.
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/
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.
