When a major science journal publishes a major climate article led by our top climate scientist–and is wise enough to make it an open access article — you MUST read it. I reviewed an early draft of “Global Temperature Change,” by James Hansen et al in the current Proceedings of the National Academy of Sciences and consider it one of the most important articles published this year — or any year — worth reading a few times.
The article is already making headlines for showing that by 2050 the Earth will be warmer than it has been for a million years, thanks to human emissions of greenhouse gases. If we take strong actions to limit further emissions starting today — what the authors call the AS [alternative scenario] — we can limit total warming from preindustrial levels to about 2°C, but even that risks sea level rise of one meter per century.
Failing to act, the authors warn, ensures far higher temperature rise, “which could yield sea level rise of several meters per century with eventual rise of tens of meters, enough to transform global coastlines.” That is “the disastrous BAU [business as usual]” case.
Equally worrisome is that “species loss under BAU has the potential to be truly disastrous, conceivably with a majority of today’s plants and animals headed toward extermination.”
The paper notes that the alternative scenario limits the severe but difficult-to-quantify risks of melting tundra and other serious carbon cycle feedbacks that Climate Progress has discussed. Yet even one more decade of inaction is likely to render that scenario “infeasible.”
The time to act is now.
Two other highlights are worth noting. First, the article sets the record straight on recent warming trends and how climate models have accurately predicted them. NASA’s press release points out, “the Earth is now reaching and passing through the warmest levels seen in the last 12,000 years. And the warming is accelerating: