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A clearer picture how climate change affects El Niño?

Filed under: — rasmus @ 28 November 2014

I still remember the first time I was asked about how climate change affects El Niño. It was given as a group exercise during a winter school in Les Houghes (in France) back in February 1996. Since then, I have kept thinking about this question, and I have not been the only one wondering about this. Now I had my hopes up as a new study was just published on the evolution and forcing mechanisms of El Niño over the past 21,000 years (Liu et al., 2014).

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  1. Z. Liu, Z. Lu, X. Wen, B.L. Otto-Bliesner, A. Timmermann, and K.M. Cobb, "Evolution and forcing mechanisms of El Niño over the past 21,000 years", Nature, vol. 515, pp. 550-553, 2014.

Unforced variations: Nov 2014

Filed under: — group @ 2 November 2014

This month’s open thread. In honour of today’s New York Marathon, we are expecting the fastest of you to read and digest the final IPCC Synthesis report in sub-3 hours. For those who didn’t keep up with the IPCC training regime, the Summary for Policy Makers provides a more accessible target.

Also in the news, follow #ArcticCircle2014 for some great info on the Arctic Circle meeting in Iceland.

Storm surge: Hurricane Sandy

Filed under: — group @ 29 October 2014

On the second anniversary of Superstorm Sandy making landfall, we are running an extract from a new book by Adam Sobel “Storm Surge: Hurricane Sandy, Our Changing Climate, and Extreme Weather of the Past and Future”. It’s a great read covering the meteorology of the event, the preparation, the response and the implications for the future.

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How do trees change the climate?

Filed under: — group @ 27 October 2014

Guest commentary from Abby Swann (U. Washington)

This past month, an op-ed by Nadine Unger appeared in the New York Times with the headline “To save the climate, don’t plant trees”.  The author’s main argument is that UN programs to address climate change by planting trees or preserving existing forests are “high risk” and a “bad bet”. [Ed. There is more background on the op-ed here]

However, I don’t think that these conclusions are supported by the science.  The author connects unrelated issues about trees, conflates what we know about trees from different latitudes, and fails to convey the main point: tropical trees keep climate cool locally, help keep rainfall rates high, and have innumerable non-climate benefits including maintaining habitat and supporting biodiversity.

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Ocean heat storage: a particularly lousy policy target + Update

Filed under: — stefan @ 20 October 2014

The New York Times, 12 December 2027: After 12 years of debate and negotiation, kicked off in Paris in 2015, world leaders have finally agreed to ditch the goal of limiting global warming to below 2 °C. Instead, they have agreed to the new goal of limiting global ocean heat content to 1024 Joules. The decision was widely welcomed by the science and policy communities as a great step forward. “In the past, the 2 °C goal has allowed some governments to pretend that they are taking serious action to mitigate global warming, when in reality they have achieved almost nothing. I’m sure that this can’t happen again with the new 1024 Joules goal”, said David Victor, a professor of international relations who originally proposed this change back in 2014. And an unnamed senior EU negotiator commented: “Perhaps I shouldn’t say this, but some heads of state had trouble understanding the implications of the 2 °C target; sometimes they even accidentally talked of limiting global warming to 2%. I’m glad that we now have those 1024 Joules which are much easier to grasp for policy makers and the public.”

This fictitious newspaper item is of course absurd and will never become reality, because ocean heat content is unsuited as a climate policy target. Here are three main reasons why. More »

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