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
8.
http://www.pewresearch.org/fact-tank/2014/02/03/10-projections-for-the-global-population-in-2050/
