Now that I am back, let's get things rolling with this piece over at Mises.org by David Evans, a mathematician, and a computer and electrical engineer who worked for the Australian government.
He starts by laying out his role in the AGW machinery and stating that he has changed his mind:
I devoted six years to carbon accounting, building models for the Australian government to estimate carbon emissions from land use change and forestry. When I started that job in 1999 the evidence that carbon emissions caused global warming seemed pretty conclusive, but since then new evidence has weakened that case. I am now skeptical.Now why exactly would someone with first hand experience go from being a true believer to a skeptic?
In the late 1990s, this was the evidence suggesting that carbon emissions caused global warming:
Carbon dioxide is a greenhouse gas, proved in a laboratory a century ago.
Global warming has been occurring for a century and concentrations of atmospheric carbon have been rising for a century. Correlation is not causation, but in a rough sense it looked like a fit.
Ice core data, starting with the first cores from Vostok in 1985, allowed us to measure temperature and atmospheric carbon going back hundreds of thousands of years, through several dramatic global warming and cooling events. To the temporal resolution then available (data points more than a thousand years apart), atmospheric carbon and temperature moved in lockstep: they rose and fell together. Talk about a smoking gun!
There were no other credible causes of global warming.
This evidence was not conclusive, but why wait until we are absolutely certain when we apparently need to act now? So the idea that carbon emissions were causing global warming passed from the scientific community into the political realm. Research increased, bureaucracies were formed, international committees met, and eventually the Kyoto protocol was signed in 1997 to curb carbon emissions.
The evidence at the time lead him to believe Global Warming was a man made phenomenon. But soon the evidence started pointing away from this:
But starting in about 2000, the last three of the four pieces of evidence above fell away. Using the same point numbers as above:
- Better data shows that from 1940 to 1975 the earth cooled while atmospheric carbon increased. That 35 year non-correlation might eventually be explained by global dimming, only discovered in about 2003.
The temporal resolution of the ice core data improved. By 2004 we knew that in past warming events, the temperature increases generally started about 800 years before the rises in atmospheric carbon. Causality does not run in the direction I had assumed in 1999 — it runs the opposite way!
It took several hundred years of warming for the oceans to give off more of their carbon. This proves that there is a cause of global warming other than atmospheric carbon. And while it is possible that rising atmospheric carbon in these past warmings then went on to cause more warming ("amplification" of the initial warming), the ice core data neither proves nor disproves this hypothesis.
- There is now a credible alternative suspect. In October 2006 Henrik Svensmark showed experimentally that cosmic rays cause cloud formation. Clouds have a net cooling effect, but for the last three decades there have been fewer clouds than normal because the sun's magnetic field, which shields us from cosmic rays, has been stronger than usual. So the earth heated up. It's too early to judge what fraction of global warming is caused by cosmic rays.
There is now no observational evidence that global warming is caused by carbon emissions. You would think that in over 20 years of intense investigation we would have found something. For example, greenhouse warming due to carbon emissions should warm the upper atmosphere faster than the lower atmosphere — but until 2006 the data showed the opposite, and thus that the greenhouse effect was not occurring! In 2006 better data allowed that the effect might be occurring, except in the tropics.
So, like a good scientist should do, once he got better information, he adjusted his beliefs in the direction that the evidence supported.
Let's return to the interaction between science and politics. By 2000 the political system had responded to the strong scientific case that carbon emissions caused global warming by creating thousands of bureaucratic and science jobs aimed at more research and at curbing carbon emissions.
But after 2000 the case against carbon emissions gradually got weaker. Future evidence might strengthen or further weaken it. At what stage of the weakening should the science community alert the political system that carbon emissions might not be the main cause of global warming?
None of the new evidence actually says that carbon emissions are definitely not the cause of global warming, there are lots of good science jobs potentially at stake, and if the scientific message wavers then it might be difficult to later recapture the attention of the political system. What has happened is that most research efforts since 1990 have assumed that carbon emissions were the cause, and the alternatives get much less research or political attention.
Unfortunately politics and science have become even more entangled. Climate change has become a partisan political issue, so positions become more entrenched. Politicians and the public prefer simple and less-nuanced messages. At the moment the political climate strongly blames carbon emissions, to the point of silencing critics.
He then goes on to assert his belief that science will win out in the end, but I personally have my doubts. There seem to be far too many scientists unwilling to follow the evidence which is increasingly pointing away from AGW and the would put a nix on all the money flowing their way.Hopefully more like him will continue to do the right thing and put a stop to the madness.
Oh and one last thing he mentioned that is very important.
Science has not progressed by calculations and models, but by repeatable observations.