Professor Ray Bates:

No. In general, I would accept the IPCC reports are being the most authoritative general voice of the climate community. At the same time, however, there is room to take into account some dissenting voices and some recent developments that have taken place since the last IPCC report in 2007.

Professor Richard Lindzen is a controversial climate scientist. I have known him quite well since the 1960s. He was at Harvard when I was at MIT and our paths crossed many times. Over the years, I have seen him and I know his scientific ability, as well as his political stance. As regards his scientific ability, almost everybody in climate science would regard him as one of the top people in the field. He was a professor at Harvard and subsequently a professor at MIT.

Professor Lindzen has a very sceptical attitude towards climate models in general. The most recent evidence on which he bases doubt about the model projections is a disagreement between the radiation from the earth as measured by satellite and the corresponding radiation from the models. His most recent paper was co-authored by Dr. Choi, who is South Korean. They published this paper in the Asia Pacific Journal of Atmospheric Sciences in 2011. I work with models, rather than observations. However, the Lindzen and Choi paper claimed that if one changes the surface temperature and looks at the corresponding change in radiation going out from the atmosphere to space, the satellite measurements indicate that the radiative response in the tropics - which constitute half the earth's surface, taking it up to 30 degrees - is stabilising. In other words, increase the temperature and one gets more radiation going into space; it brings it back to where it was. They claim the models are showing that the radiative response is destabilising. Therefore observations show it is stabilising, while models show it is destabilising.

I am in no position to judge whether these observations are right or wrong, but I wrote a paper in 2012 which is quoted in my report. It examined the consequences of these observations, which are very strong if they are valid. The models would be overestimating climate sensitivity. Nobody in the climate field denies that increasing greenhouse gases has a warming effect on the earth. This is universally accepted by every climate scientist without exception. However, the question of the actual extent of warming that one gets from a doubling of CO₂ is something that varies quite a bit from model to model.

In the past 15 years, for example, if one looks at the projections of the models, all the projections are for fairly significant warming. The observations, however, show no warming essentially since 1998. This does not mean that global warming has stopped, but it indicates that there is something going on that we do not understand. The models are projecting continual warming, while the observations have been flat since 1998. The most likely explanation of this is another paper by Tong and Zhao, who are two Chinese-American scientists. They have done a detailed study of the Atlantic multi-decadal oscillation, which is an oscillation of the Atlantic sea surface temperatures with a period of approximately 70 years and a peak amplitude of about 0.4^o Celsius. During the period when maximum global warming was occurring up to the 40 years previous to 1994, the Atlantic multi-decadal oscillation was in a period of increasing temperature. Now it is in a phase of decreasing temperature.

The papers by Tong and Choi suggest, or claim, that 40% of the observed warming prior to 1998 was due to the rising phase of the Atlantic multi-decadal oscillation. The current plateau that we are seeing in the global temperature is due to the fact that the Atlantic multi-decadal oscillation is now in a declining or cooling phase. If their results are valid, it would mean that we could have a steady temperature for a while before it starts to go up again when the Atlantic multi-decadal oscillation gets into its positive phase again.