Predicting Short-Term Change
August 10, 2007 | Posted by Lisa Moore in Scientists & Methods
The author of today"s post, Lisa Moore, Ph.D., is a scientist in the Climate and Air Program.
Climate models are usually run far into the future, projecting temperature changes to the end of the century. Over the long term, the effects of greenhouse gases overwhelm all other factors. But climate can have substantial "short-term internal variability" - for example, temperature shifts due to El Niño and La Niña. Climate models have never been able to predict this internal variability - until now.
A paper in today's issue of Science ("Improved Surface Temperature Prediction for the Coming Decade from a Global Climate Model") describes a new and improved climate model that predicts both greenhouse warming and internal climate variability. The model's hindcasts are substantially better than earlier model results. (For more on hindcasts, see the post "Climate Models: How Good Are They?").
When the authors ran their model into the future, they found that internal variability would offset global warming until 2008, but the new model (like older models) predicts significant warming during the coming decade. At least half the years after 2009 are predicted to exceed the warmest year currently on record.
So while the improved predictability of short-term variability is welcome, the long-term picture remains the same. The world is getting warmer.
3 Responses
Comment from kenzrw
August 10th, 2007 at 5:51 pm
Quite interesting. I've never read much on 'internal variablility' before, but I'm glad the new and improved climate model takes this natural variability into account. I've always knew that an El Nino event helped cause the 1998 heat, but never though of this as 'internal variability' before. Since the article says this natural variability offset global warming somewhat in the past, the model says that effect won't be able to offset most of the warming past 2008, is that correct? So, instead of warming .5 degree, for instance, a natural internal variability event could lower that warming to, say, .3 degrees, correct? Either way, it's getting warming.
Comment from Lisa Moore
August 13th, 2007 at 4:29 pm
Hi kenzrw,
The model projects that cooling in the tropical Pacific will slow greenhouse warming over the next couple of years. After that, though, rapid warming kicks in again, with temperatures 0.3 degrees C higher by 2014 than they were in 2004. That's a LOT of warming in just a decade!
Predicting these short-term temperature changes is a fascinating challenge; we should be seeing more and more research about this in coming months.
Comment from Lisa Moore
August 21st, 2007 at 12:05 pm
RealClimate just posted a summary of this paper. The relevant paragraphs are in the section "Prediction vs. Projections".
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