It is good news that the authors of the PNAS paper Reconciling anthropogenic climate change with observed temperature 1998 – 2008 (Kaufmann et al. 2011) recognise that there has been no global temperature increase since 1998. Even after the standstill appears time and again in peer-reviewed scientific studies, many commentators still deny its reality. We live in the warmest decade since thermometer records began about 150 years ago, but it hasn’t gotten any warmer for at least a decade.
The researchers tweak an out-of-date climate computer model and cherry-pick the outcome to get their desired result. They do not use the latest data on the sun’s influence on the Earth, rendering their results of academic interest only.
They blame China’s increasing coal consumption that they say is adding particles into the atmosphere that reflect sunlight and therefore cool the planet. The effect of aerosols and their interplay with other agents of combustion is a major uncertainty in climate models. Moreover, despite China’s coal burning, data indicate that in the past decade the amount of aerosols in the atmosphere has not increased.
The researchers seek to explain the temperature standstill between 1998 and 2008. They say that the global temperature has increased since then.
This is misleading. There was an El Nino in 2010 (natural cyclic warming) but even that did not raise temperatures above 1998. In fact the standstill has continued to 2010 and 2011 appears to be on course to be a cooler year than any of the preceding ten years.
Tweaking computer models like this proves nothing. The real test is in the real world data. The temperature hasn’t increased for over a decade. For there to be any faith in the underlying scientific assumptions the world has to start warming soon, at an enhanced rate to compensate for it being held back for a decade.
Despite what the authors of this paper state after their tinkering with an out-of-date climate computer model, there is as yet no convincing explanation for the global temperature standstill of the past decade.
Either man-made and natural climatic effects have conspired to completely offset the warming that should have occurred due to greenhouse gasses in the past decade, or our estimation of the ‘climate sensitivity’ to greenhouse gasses is too large.
This is not an extreme or ‘sceptic’ position but represents part of the diversity of scientific opinion presented to the IPCC that is seldom reported.