A frequent argument made by climate contrarians is that global warming hasn't yet resulted in unbearable climate change consequences, and therefore we have nothing to worry about. In a talk recorded by ReasonTV, Matt Ridley offers up several different examples of this line of thinking, arguing that climate change thus far has had some positive consequences and that fossil fuels are just great, implying that we should continue to consume them without worry.
However, this argument misses a key point – climate scientists aren't terribly concerned about the current state of the Earth's climate. If we were to stabilize atmospheric CO2 levels below 400 parts per million (ppm) – a level we are rapidly approaching – most people would be thrilled about that (especially if those levels eventually drop to somewhere around 350 ppm). The concern is that human CO2 emissions and the resulting global warming show no signs of slowing (Figure 1).
Figure 1: Estimated expected warming for the RCP scenarios in a most likely case world with 3°C equilibrium climate sensitivity (see this post for background and details).
The three higher warming scenarios in Figure 1 (red, green, and purple) describe the future that Ridley advocates for, where we see several more degrees of global surface warming over the next century. That is the future we are concerned about.
Most of Ridley's ReasonTV talk focuses on a claim that we've previously examined, that the planet is 'greening' and therefore more CO2 is great for plants. Overall the argument that CO2 is plant food is a gross oversimplification. It's true that when all else is held relatively constant, for example in a greenhouse, adding CO2 to the environment tends to increase plant growth. However, when we add more CO2 to the atmosphere, it changes the climate. More extreme weather results, like heat waves, bush fires, droughts, and floods - conditions which are obviously not favorable to plant growth. As John Mason has discussed,
"A key constraint of the carbon fertilization effect on the ground (and not in the controlled conditions of a greenhouse or laboratory) is that it would be operating in situations where other variables, essential to plant growth, may not play ball. It's a long list when one includes all the various minerals and trace-elements but key factors are major nutrients such as phosphorus, potassium, nitrogen and so on. CO2 is plant-food but so are these elements and they are essential, as any serious vegetable-grower will tell you."
It's just not as simple as 'more CO2 = more plant growth'; not even close. To argue otherwise, Ridley focuses on some studies of global Net Primary Production, which is essentially a measurement of plant growth. These studies have shown that over the past few decades, the planet has become greener. Great news, right? Well, that depends on where the greening is happening and which plants are thriving, but more importantly, Ridley fails to mention that the greening trend has already slowed down, and possibly even reversed (Figure 2).
Figure 2: Net primary production change measurements (in petagrams [1015 grams] of carbon per year) from Nemani et al. 2003 (blue), Zhao and Running 2010 (red), and Potter et al. 2012 (green).
The plants we're most concerned about are food crops, particularly staple crops like maize. On this subject, Ridley discusses the role technology has played in making agriculture more efficient and productive, which is indeed a very good thing. But again, we're concerned about what future climate change will do to that trend of increased agrigultural productivity. For example, Hawkins et al. (2012) examined maize yields in France and found that improved agricultural technology has increased crop yields, but hotter temperatures are taking a toll, and the increase has begun to slow (Figure 3).
Figure 3: French maize yields from FAOSTAT (black points) and empirical model predictions for the technology trend (grey shading) and expected yield (red shading) with total uncertainties (red lines), considering both temperature and precipitation. The black error bar indicates the forecast for 2011, assuming a flat technology trend since 2010. For the 2016-2035 periods, the boxes show the 25th-75th percentiles and the whiskers indicate the 5th and 95th percentiles. The yield projections assume a flat technology trend and are shown for both climatological precipitation (left) and precipitation constrained by historical correlations between temperature and precipitation (right).
In particular, note the low maize yield in 2003, associated with the major heat wave that summer. The projections for 2016—2035 in blue and red demonstrate that climate change is anticipated to decrease crop yields unless technological improvements can offset the effects of increased heat.
So what happens if monthly heat records become 12 times more frequent, as Coumou et al. (2013) predict will happen within 30 years unless we take serious action to reduce our greenhouse gas emissions? What happens when other types of extreme weather like droughts and floods increase? Will farming technological advances be able to offset the extreme weather impacts on crop production? Will the global greening trend be replaced by a browning trend?
Those future climate impacts are what we're concerned about. Arguing that so far the planet has become greener is irrelevant. It does not address climate scientists' concerns.
At the end of his talk, Ridley discussed an anecdote which apparently makes him feel comfortable about advocating that we continue to rely on fossil fuels and accelerate the greenhouse effect. The anecdote dealt with an island in the Arctic that he visited several decades ago, which did not have any polar bears at the time, but which does now.
Ridley correctly noted that while there may be more polar bears now than there were several decades ago (their populations were not accurately monitored until fairly recently), that is because polar bear hunting is now strictly regulated, and was not in the past. However, according to a 2009 report by the IUCN Polar Bear Specialist Group, of the 19 recognised subpopulations of polar bears, 8 are in decline, 1 is increasing, 3 are stable and 7 don’t have enough data to draw any conclusions. This is a marked decline since just 2005 (Figure 4).
Figure 4: Subpopulation status of polar bears for 2005 and 2009 (Source: Polar Bear Specialist Group)
Again, the concern is not current conditions, it's future conditions. Arctic sea ice is critical for polar bears to hunt, and Arctic sea ice extent and volume are in the midst of a death spiral. That dangerous trend is why polar bears are considered a threatened species, and why an American court recently upheld that designation against a challenge by the State of Alaska and industry interests.
Ridley has a history of being blindsided by events he did not foresee, for example when the bank he chaired failed and had to be bailed out by the British government. Ridley explained,
"We were hit by an unexpected and unpredictable concatenation of events."
Of course, Ridley isn't the only climate contrarian to make the mistake of focusing on current impacts while ignoring those to come in the future. For example, Roger Pielke Jr. often focuses on the fact that according to the IPCC Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX), certain types of extreme weather have not yet increased, like drought frequency in the USA. However, this misses the SREX conclusions about future climate impacts, which notes for example that droughts will likely intensify in the USA.
In a more recent example, just recently Anthony Watts said in an interview that "catastrophic predictions of the future just haven’t held up," but climate scientists don't expect catastrophic climate impacts to occur until later this century.
It's a common mistake among climate contrarians because it seems like a logical and reassuring argument – climate change hasn't yet resulted in terribly negative consequences, so maybe it's nothing to worry about. Unfortunately that conclusion flies in the face of a vast body of evidence indicating that if we continue on our current course, the climate consequences will be very bad, and potentially catastrophic.
The argument is like a diagnosed cancer sufferer claiming he's okay because he doesn't yet feel the effects. In truth there are a number of troubling things already underway – ocean acidification, the collapse of coral reefs, stronger and more frequent extreme weather events, sea level rise, sea ice and ice sheets melting, permafrost thawing, etc. We simply cannot allow these climate trends to continue just because we haven't yet felt the worst effects.
Posted by dana1981 on Thursday, 4 April, 2013
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