Sea-Level Rise

I previously posted a summary of the water-related conclusions from the new National Climate Assessment, recently released after three years of writing, review, and analysis. The following “findings” are a broader summary of the results from the newly released National Climate Assessment (NCA). They are by no means a full summary: far more detail can be found in the chapters and the regional syntheses, but these are noteworthy conclusions. (Note, thanks to Tim Smith – Sustainable Water Resources Coordinator – for highlighting these. The page numbers refer to the NCA Summary) 1. Global climate…

Snapshots from the New National Climate Assessment After three years of intensive effort, research, writing, and review by hundreds of climate scientists, the latest update of the U.S. National Climate Assessment was released today. It includes many long, carefully prepared sectoral and regional studies, and covers the massive range of effects of climate change on the nation, including both changes already observed and expected in the future. There are hundreds of pages of information, observations, projections, and conclusions to absorb – almost all of it bad news. Here, in short form and in…

The evidence from real-world observations, sophisticated computer models, and research in hundreds of different fields continues to pile up: human-caused climate change is already occurring and will continue to get worse and worse as greenhouse-gas concentrations continue to rise. Because the climate is connected to every major geophysical, chemical, and biological system on the planet, it should not be surprising that we are learning more and more about the potential implications of these changes for a remarkably wide range of things. And while it is certainly possible – even likely – that…

The planet has passed a disturbing landmark, a marker on a continuing highway to climate disruption. On May 9th, the NOAA and the Mauna Loa observatory reported that atmospheric CO2 levels touched 400 parts per million. Before humans started burning fossil fuels, they were around 280 parts per million. Mauna Loa measurements of carbon dioxide. From http://keelingcurve.ucsd.edu/   The last time atmospheric CO2 was at 400 parts per million was during the ancient Pliocene Era, three to five million years ago, and humans didn’t exist. Global average temperatures were 3 to 4 degrees C warmer…

Sometime, about one year from now, the front pages of whatever decent newspapers are left will carry a headline like the one above, announcing that for the first time in human existence (or in nearly a million years, or 3 million years, or 15 million years), the global atmospheric concentration of carbon dioxide – the principal gas causing climate change – will have passed 400 parts per million. That’s a significant and shocking figure. Unfortunately, it is only a temporary marker on the way to even higher and higher levels. Here (Figure 1 below) are the most recent (March 2013) data from the…

One of the most important and threatening risks of climate change is sea-level rise (SLR). The mechanisms are well understood, and the direction of changes in sea-level is highly certain – it is rising and the rate of rise will accelerate. There remain plenty of uncertainties (i.e., a range of possible outcomes) about the timing and rate of rise that have to do with how fast we continue to put greenhouse gases in the atmosphere, the responses of (especially) ice sheets in Greenland and Antarctica, and the sensitivity of the climate. Even little changes can have big consequences. As we saw…