Weatherdem's Weblog

Bridging climate science, citizens, and policy

Arctic Is Warmest In Over 2000 Years

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Research conducted in the post-2007 IPCC 4AR world continues to demonstrate how much effect humans’ climate forcing is having.  The latest is an article in the prestigious journal Science, which shows that temperatures in the Arctic in the year 2000 were significantly higher than any temperature there in the past 2,000 years.  More strikingly, the temperature trend that was present for 1,900 years took a dramatic shift in the last 100 years of that time period.  Separate research has shown that the polar regions of Earth have warmed faster than any other part of the globe through the current day.  Though this study doesn’t address post-2000 Arctic temperatures, it is likely safe to assume that the multi-millenial trend identified in this Science study has only continued.

The main climate forcing for the Arctic in the past has been Earth’s position and axial tilt with respect to the sun.  The Arctic was slowly cooling over time due to the Earth’s location with respect to the sun.  In the last 200 years, a new forcing mechanism has unambiguously reversed that cooling.  People’s burning of fossil fuels has reversed nearly 2,000 years of cooling – we have forced the climate system in a more extreme way than natural forces could accomplish over millenia.  The natural cooling is likely ongoing, but is masked by our forcing signal that appears in this and other temperature trends.  Since 1800, temperatures in the Arctic have increased by 1.2C: where it was once -0.8C anomalously cool, it is now nearly 0.4C anomalously warm.

That warming has caused the recent record low ice extents of Arctic sea ice.  My last post on Arctic sea ice conveyed that the Arctic has likely entered a new “normal” phase: summer sea ice extent has fallen more than two standard deviations below the 1979-2000 climatological average during the past three years.  The temperatures anomalies that the Science article researchers identify manifest themselves as anomalous heat content in both the ocean and the atmosphere of the Arctic.  As the ocean and atmosphere warm up a little, ice has a harder time reforming every boreal winter.  A little more warmth, a little harder to refreeze sea water.  Like most non-linear systems, this process may not manifest itself physically for many cycles.  Then, all of a sudden, a drastic change becomes apparent.  A non-linear tipping point may have been passed in the Arctic.  I think it will be difficult to reform the amount of ice that was commonly seen in the middle and latter portions of the 20th century.  The ocean water has simply absorbed too much thermal energy at this point.  A great deal of that absorbed thermal energy has to be transferred to the atmosphere every winter if sea water is to re-freeze.

This news comes after I attended a decent talk at the University of Colorado at Boulder regarding President Obama’s energy and climate policy thus far into his still young presidency.  One of the topics of discussion was the Waxman-Markey legislation (H.R. 2454 – the American Clean Energy and Security Act of 2009).  Scientists and policy makers are concluding that the goals of W-M won’t go far enough to mitigate the effects of climate change.  Those warmer temperatures around the Arctic?  They help to contribute to melting land-based glaciers in addition to sea ice.  Those processes will continue to speed up beyond pre-AR4 predictions.  If W-M is the “best” legislation that can come out of the more liberal chamber of Congress, we’re in for a century (and more) of much more expensive adaptation, ecosystem disruption and collapse, and quite literally governmental and societal collapse.

I’ll have more on the talk in an upcoming post.  For now, this study demonstrates that we are nearly out of time to act if we hope to avoid Trillions of dollars of future costs to adapt.  We can instead spend much less money – on the order of billions to mitigate climate change effects.  The best news?  Many of those mitigation billions actually have a negative cost associated with them – they more than pay for themselves on short time frames.  The choice is easy.


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