Sunday, July 19, 2009

The role of solar radiation in climate change

Science Daily: A special volume of the Journal of Geophysical Research reviews the growing research field of “global dimming” and “global brightening” in over 20 articles. These phenomena, supposedly human-induced, control solar radiation incident at the Earth’s surface and thus influence climate.

…Investigating which factors reduce or intensify solar radiation and thus cause “global dimming” or “global brightening” is still very much a nascent field of research. The American Geophysical Union (AGU) has now published a special volume on the subject which presents the current state of knowledge in detail and makes a considerable contribution to climate science.

…In analyzing more recently compiled data, however, Wild and his team discovered that solar radiation has gradually been increasing again since 1985. In a paper published in “Science” in 2005, they coined the phrase “global brightening” to describe this new trend and to oppose to the term “global dimming” used since 2001 for the previously established decrease in solar radiation. Only recently, an article in the journal Nature, which Wild was also involved in, brought additional attention to the topic of global dimming/brightening.

… A further challenge for the researchers is to incorporate the effects of global dimming/brightening more effectively in climate models, to understand their impact on climate change better. After all, studies indicate that global dimming masked the actual temperature rise – and therefore climate change – until well into the 1980s. Moreover, the studies published also show that the models used in the Intergovernmental Panel on Climate Change’s (IPCC) fourth Assessment Report do not reproduce global dimming/brightening adequately: neither the dimming nor the subsequent brightening is simulated realistically by the models. According to the scientists, this is probably due to the fact that the processes causing global dimming/brightening were not taken into account adequately and that the historical anthropogenic emissions used as model input are afflicted with considerable uncertainties….

The sun's corona, shot by Rogilbert, who has released the image into the public domain


Duncan said...

Stop it.
The science is settled.
The models are accurate enough to predict climate 100 years in the future, and regional weather 100 years from now too.

Suggesting there's anything scientists don't know is treason against the Earth.

Brian Thomas said...

I posted this, not because I was eager to help the denialists, but because it appears to be interesting research from a credible source. The ETH in Zurich is no hotbed of denial, I can assure you.

Also, I think our zeal to combat climate change -- my zeal, too -- should not blind us to the tremendous uncertainties we face. I agree with you that the role of anthropogenic forcings is virtually certain. But a few levels down from that, there is tremendous uncertainty.

As for the models accuracy, yes, we can make predictions, but we don't know how good they'll be. Acknowledging this shouldn't be construed as bashing the models altogether. In fact, the modelers I've spoken to don't sound nearly so confident.

Properly accounting for global dimming and brightening is one such area where the models need improvement. At least according to this issue of the Journal of Geophysical Research.