by Dana Nuccitelli, via Skeptical Science
In April of 2012, 49 former NASA employees sent a letter to the current NASA administrator requesting that he effectively muzzle the climate scientists at NASA Goddard Institute for Space Studies (GISS). None of those former NASA employees have conducted any climate science research, but based on their own lack of understanding of the subject, they objected to the conclusions drawn by the climate experts at NASA GISS. This letter drew media attention because folks who have worked at NASA are well-respected (and rightly so), but there was really no substance to it, or any particular reason to lend it credence. Astronauts and engineers are not climate experts.
Now in January of 2013, a group of 20 “Apollo era NASA retirees” has put together a rudimentary climate “report” and issued a press release declaring that they have decided human-caused global warming is not “settled” and is nothing to worry about. This time around they have not listed the 20 individuals who contributed to this project, but have simply described the group as being:
“…comprised of renowned space scientists with formal educational and decades career involvement in engineering, physics, chemistry, astrophysics, geophysics, geology and meteorology. Many of these scientists have Ph.Ds.”
The project seems to be headed by H. Leighton Steward, a 77-year-old former oil and gas executive. The press release also links the NASA group to his website, “co2isgreen”, which also has an extensive history of receiving fossil fuel industry funding.
This story can be summed up very simply: a group of retired NASA scientists with no climate science research experience listened to a few climate scientists and a few fossil fuel-funded contrarian scientists, read a few climate blogs, asked a few relatively simple questions, decided that those questions cannot be answered (though we will answer them in this post), put together a very rudimentary report, and now expect people to listen to them because they used to work at NASA. It’s purely an appeal to authority, except that the participants have no authority or expertise in climate science.
Answering the NASA Retirees’ Questions
Most of the group’s report is devoted to summarizing some basic aspects of climate science, such as the greenhouse effect. At the end it lists seven “conclusions”, most of which are questions they claim “are still to be resolved”, but in reality are generally simple to answer.
1) How really well known is the global temperature of the earth over the past century?
Quite really well known. The accuracy of the surface temperature record has been confirmed by many different studies using a variety of different approaches, including by natural thermometers and satellites. There is very little difference between the results of different groups analyzing the surface temperature data (Figure 1).
2) How important to the factors that determine the surface temperature of the earth are the human related increases of CO2?
Human greenhouse gas emissions are the dominant cause of global warming. The science is entirely settled on this question, which simply boils down to physics. Long-term global warming is caused by a global energy imbalance. Human greenhouse gas emissions are responsible for by far the largest such energy imbalance over the past century. The graph below (Figure 3), is taken from Tett et al. 2000 (T00, dark blue), Meehl et al. 2004 (M04, red), Stone et al. 2007 (S07, light green), Lean and Rind 2008 (LR08, purple), Huber and Knutti 2011 (HK11, light blue), Gillett et al. 2012 (G12, orange), and Wigley and Santer 2012 (WS12, dark green).
3) What exactly are the true feedback effects and how do they vary?
There are a number of different climate feedbacks which amplify or dampen global warming. The NASA document accurately summarizes their net effect.
“The net effect, which includes feedbacks) on the temperature anomaly from the IPCC (AR4) was … 2.0 – 4.5 K”
By itself, a doubling of atmospheric CO2 will cause an energy imbalance sufficient to ultimately warm global surface temperatures about 1.2°C. Through a variety of different types of studies, climate scientists have concluded that the net effect of the various temperature feedbacks will amplify that warming to somewhere in the range of 2 to 4.5°C in response to doubled CO2.
4) Since the 1988 Hansen paper and presentation to Congress, through the IPCC 2000 and subsequent projections of the global temperature anomaly, the models have consistently over-projected the actual measured temperature anomalies in the subsequent years.
This statement, derived from a blog post, is simply incorrect. As we at Skeptical Science have shown several times, the IPCC temperature projections have been exceptionally accurate (Figure 4).
Conclusion 4 in the document also incorrectly states that “the IPCC projections are intended to represent the worst-case scenario.” The IPCC projections are based on a wide variety of human greenhouse gas emissions scenarios, not simply a single worst-case scenario. Given that many climate variables are changing faster than the IPCC anticipated, it would make for a pretty terrible worst case scenario.
5) What accounts for some of the observed differences between the steady increase in CO2 concentrations over the last century and the more erratic changes in estimated global temperature anomaly?
Cooling from human aerosol emissions offset warming from human greenhouse gas emissions in the mid-20th century, and on top of that there is natural internal variability in the climate system, as Kevin C’s video illustrates.
6) What are the relative effects of natural climate oscillations such as the El Nino Southern Oscillation, (ENSO), the Pacific Decadal Oscillation (PDO), and the Atlantic Multi-decadal Oscillation (AMO) on the earth’s temperature trends? Are they compensating for the radiative forcing of CO2 (and other GHG) increases?
These are some of the contributors to the short-term natural internal variability mentioned in the answer to the last question. No, natural variability is not ‘compensating’ for the radiative forcing (global energy imbalance) caused by greenhouse gases. Recent research by Sedláček & Knutti (2012) found that warming caused by internal variability creates a very patchy pattern, whereas we observe a very smooth pattern of warming, consistent with an external forcing like an increased greenhouse effect. However, the ocean cycles mentioned in this question have caused a short-term dampening of global surface warming over the past decade or so.
7) Why is it assumed that, aside from the more obvious impacts of significant sea level rise on existing infrastructure, that the net effect of more CO2 is negative? After all, CO2 is often added to commercial greenhouses to promote plant growth.
This is not an assumption, it is the result of a wide body of scientific research. More CO2 means more global warming, which means more climate change, which means more extreme weather, like more heat waves and droughts, which does not bode well for plant growth or for most other life on the planet. Species are already going extinct at a relatively rapid rate. And on top of climate change, there’s the damage CO2 causes via ocean acidification, global warming’s evil twin.
These are not difficult questions, in fact we have answered them all here on Skeptical Science.
Risk Management – Uncertainty is not Your Friend
After failing to do more than the most rudimentary climate research, the NASA retirees wrongly conclude that uncertainty can be used to justify inaction.
“Despite claims of consensus and other appeals to authority, no one knows these answers. Once politics is removed, the evidence so far (2011) is that the actual net effect is low or uncertain (considering multiple known and potential feedbacks). As such, aggressive and extraordinarily far-reaching steps by governments to reduce production of CO2 is not warranted.”
This conclusion illustrates a risk management failure which is very common amongst climate contrarians. It’s no different than saying “I don’t think that I’ll be in a car accident, so I won’t purchase auto insurance.” The average American has a 30 percent chance of being involved in a serious automobile accident in his or her lifetime, and the odds of very dangerous and damaging climate change are even higher if we continue on a business-as-usual path – in fact that is the most likely scenario.
Climate contrarians like these NASA retirees essentially believe that the best case scenario will occur, that the net climate feedback and sensitivity will be near the low end of the possible range, and that we will be able to cope with future climate change. That is a possibility, but the best case scenario is only one possible outcome, and thus represents a very low overall probability of occurring. And when we fail to prepare for or prevent the worst case scenario, or even the most probable scenario, bad things happen.
Appealing to Authority Requires Actually Having Authority
Ultimately the NASA Apollo-era retirees expect the public to defer to their opinions on climate change, despite the fact that they have failed to do more than the most basic climate research and do not understand the most fundamental aspects of risk management (which is rather strange, since Apollo 13 was a good lesson in preparing for the worst case scenario).
In reality many of the questions they believe nobody has answered are actually settled science. We know humans are causing global warming, we know there is also natural variability in the climate system, and we know the climate consequences will be bad if we continue on our present course. Just how bad is an open question, which depends in large part on how quickly we reduce our greenhouse gas emissions. However, these NASA retirees are asking us to delay action in the hopes that the best case scenario will occur. This is a total risk management failure, because if they are wrong and the best case does not come to fruition, we will face some nasty consequences, and there will be very little that we can do about it.
As with the last NASA retiree letter, there is no reason why we should pay heed to this document, and very good reasons why we should reject its conclusions. We are again left wishing that these retirees would leave the climate science to the real climate experts at NASA, who are some of the best in the world.
— Dana Nuccitelli, reprinted with permission from Skeptical Science