A Climate Change Christmas

Did everyone enjoy wearing shorts and t-shirts in the Northeast on Christmas Eve yesterday? Yeah, that’s just great. Of course, such freakish temperatures are not entirely about climate change–El Niño and luck are part of it too–but they are indeed about climate change as 2015 sets another record for the world’s warmest year on record.

Of course, climate change isn’t just about how hot it is outside during the winter. It’s also about the widespread transformation of ecosystems, so this Christmas let’s read a bit on the impact on trees in the Southwest.

In a troubling new study just out in Nature Climate Change, a group of researchers says that a warming climate could trigger a “massive” dieoff of coniferous trees, such as junipers and piñon pines, in the U.S. southwest sometime this century.

The study is based on both global and regional simulations — which show “consistent predictions of widespread mortality,” the paper says — and also an experiment on three large tree plots in New Mexico. The work was led by Nate McDowell of the Los Alamos National Laboratory who conducted the research along with 18 other authors from a diverse group of universities and federal agencies, including the U.S. Geological Survey.

“We have fairly consistent predictions of widespread loss of piñon pine and juniper in the southwest, sometime around 2050,” said McDowell. The paper concludes that the consequences could be vast, citing “profound impacts on carbon storage, climate forcing, and ecosystem services.”

The study examined both an extreme warming scenario — which recent climate policies suggest we may be able to avert — and also a more modest scenario that would likely bring temperatures above 2 degrees Celsius above pre-industrial levels by the year 2100, but not necessarily by that much. The more extreme scenario was certainly worse for these trees, but even under the moderate scenario, the negative results were merely “delayed by approximately one decade,” the study found.

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Taking it all into account, then, the study concludes that there is “a high likelihood that widespread mortality” of these types of forests will occur by 2100. So many trees could die and decompose, in fact, that the study suggests that 10 gigatons of carbon — equivalent to 36.67 gigatons of carbon dioxide — could be emitted to the atmosphere as a result, in forests across the globe. That would amounting to a positive feedback that would worsen human-caused climate change; indeed, the number is pretty similar to one year’s worth of the globe’s current fossil fuel emissions.

Overall, the news worsens a prior scientific outlook which had already suggested that U.S. forests, as a whole, could store less carbon in the future than they currently do — and thus, offset fewer U.S. emissions.

I think I need that smoking Santa again.