Is the pace of climate change slowing down?

Question: The pace of increase in surface air temperatures appears to have slowed slightly in past 15 years or so. What does this mean about climate change? Is it slowing down?

David Wolfe, Faculty Fellow and Chair of the Climate Change Focus Group, Atkinson Center for a Sustainable Future and Professor, Department of Horticulture replies:

Click graph for larger view.

Click graph for larger view.

There is much natural year-to-year variability in the climate system. So looking at the past several years by itself can be misleading, sort of like looking at ups and downs in the stock market during a single day and expecting this to reveal long-term trends.

It is important to realize that during the past 15 years or so the planet has continued to warm at an alarming pace based on many indicators. But more of the warmth has been captured by the oceans than expected, with sea warming occurring into deeper layers. The annual relative magnitude of how much of the planet’s warming manifests as surface air temperature increase vs. ocean heating is complicated and we are still learning.

The graph on the right indicates that historically most of the global warming has occurred in the oceans. Ocean warming is the primary cause of sea level rise due to a phenomenon known as thermal expansion of sea water. Oceanic warming has very long term implications because it will be very slow to reverse this trend. Even if we stopped emitting all greenhouse gases today, global warming would remain a problem for some time because of oceanic warming.

There may be other nuances of the climate system causing the recent variation in air temperature increase, but there are no doubts within the Intergovernmental Panel on Climate Change (IPCC) and broader scientific community that the long term trend is for continued warming of both air and sea temperatures, with many troubling likely impacts on natural ecosystems, food security in some regions, coastal and other infrastructure, and human well-being.



Category: Climate Change Q&A

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