A Los Angeles Times story ("Global warming 'hiatus' puts climate change scientists on the spot") on September 22 contained significant missteps that place a greater emphasis on the challenge of explaining recent global warming data than most scientists consider warranted. Current natural influences appear to favor cooling, but human influence has overpowered this trend. Variations like these are an expected part of any long-term trend, and the mechanisms that are likely behind the shift are known.
The following is a guest post by Climate Nexus (text in PDF format here):
L. A. Times Overhypes Recent Warming Trends
Yesterday the L. A. Times covered the recent apparent slowdown in the rate of surface warming. The story got many facts right, including the possible reasons for the phenomenon. It mentioned factors such as ocean heating, accelerated sea level rise, and record Arctic ice melt that show the planet as a whole is still warming. It also made clear that the IPCC is more certain than ever that warming over the last 50 years is largely due to human influence. However, a few significant missteps placed a greater emphasis on the challenge than most scientists consider warranted.
When warming rates are put in perspective, we can see the facts.
- Human influence has overpowered natural influences, not the other way round as Dr. Judith Curry suggests.
- Scientists don’t consider recent trends a “glaring discrepancy.” Fluctuations like this one are expected and align with many known mechanisms.
Current natural influences appear to favor cooling, but human influence has overpowered this trend. Solar radiation is at an extreme low, and La Niña conditions have persisted for far longer than normal. Volcanic activity and industrial activity have emitted light-reflecting particles. All of these factors exert a cooling influence. Yet the planet hasn’t cooled. We’ve seen the hottest decade ever, marked by record-breaking extremes. Dr. Curry’s statement mischaracterizes the forces at play, making it seem as if current conditions are “natural” and have “overpowered” the warming trend. Actually, current conditions represent strong evidence of human influence.
Variations like these are an expected part of any long-term trend, and the mechanisms that are likely behind the shift are known. Current trends are far from a “glaring discrepancy,” and scientists are only “pressured” and “vexed” to the extent that they have to field questions from those interested in creating drama where little exists.
There are certainly areas where further research would be useful – for example, temperature measurement of the deep ocean is one field where scientists are just scratching the surface of what we can learn. But this is a far cry from the state of confusion that the L. A. Times article and similar pieces imply.
Scientists know that a combination of natural factors has contributed to the reduction in the rate of surface warming, and they also know that much of the surface warming has been temporarily redirected to the deep oceans. Studies of variation have shown that surface warming slowdowns of a decade or more are possible due to natural variability, and that such variations don’t change the trend.
Long-term climate projections remain unchallenged by this short-term shift, while climate impacts highlight the urgent need for action.
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Some earlier Climate Nexus posts: