James Hansen: We Have a Little More Time After All (Whew!)

“Contrary to the impression favored by governments, the corner has not been turned toward declining emissions and GHG amounts…. Negative CO2 emissions, i. e., extraction of CO2 from the air, is now required.”

– James Hansen, “Young People’s Burden.” October 4, 2016.

“The ponderous response of the climate system also means that we don’t need to instantaneously reduce GHG amounts.”

– James Hansen, “We Hold Truths to be Self-Evident“ December 2,  2016.

What a difference a few months make!

Just in time for holiday season, and for the Trump Administration, the father of the climate alarm, formerly a climate scientist with NASA/GISS, and now a full-time scientist/activist, has ameliorated his grand climate alarm. The 10-year ultimatum announced in 2006, made more dire in 2009 and since, is now moderated.

This October, we were told that the net concentration of man-made greenhouse gases in the atmosphere must go negative. Now, “we don’t need to instantaneously reduce GHG amounts.” A climate scientist might want to see what is going on behind the scenes with Dr. Hansen’s math and models.

Maybe the climate can survive Donald Trump after all!

Here is the history:

Old View (July 2006):

“We have at most ten years—not ten years to decide upon action, but ten years to alter fundamentally the trajectory of global greenhouse emissions” he wrote in his July 2006 review of Al Gore’s book/movie, An Inconvenient Truth. “We have reached a critical tipping point,” he assured readers, adding “it will soon be impossible to avoid climate change with far-ranging undesirable consequences.”

Revised View–Worse Than Thought (2009)

Several years later, with the publication of his 2009 manifesto Storms of My Grandchildren: The Truth about the Coming Climate Catastrophe and Our Last Chance to Save the Planet, he shared “some bad news” (p. 139) with readers:

The dangerous threshold of greenhouse gases is actually lower than what we told you a few years ago. Sorry about that mistake. It does not always work that way. Sometimes our estimates are off in the other direction, and the problem is not as bad as we thought. Not this time.

“The climate system is on the verge of tipping points,” Hansen stated (p. 171). “If the world does not make a dramatic shift in energy policies over the next few years, we may well pass the point of no return.”

Also in 2009, he told the press:

We cannot afford to put off [climate policy] change any longer. We have to get on a new path within this new administration. We have only four years left for Obama to set an example to the rest of the world. America must take the lead.

Revised View–Need to Go Emissions Negative (October 2016)

“Contrary to the impression favored by governments, the corner has not been turned toward declining emissions and GHG amounts.  The world is not effectively addressing the climate matter, nor does it have any plans to do so, regardless of how much government bureaucrats clap each other on the back.…. Negative CO2 emissions, i.e., extraction of CO2 from the air, is now required.”

New View (December 2016):

“Stopping human-made climate change is inherently difficult, because of the nature of the climate system: it is massive, so it responds only slowly to forcings; and, unfortunately, the feedbacks in the climate system are predominately amplifying on time scales of decades-centuries.

The upshot is that there is already much more climate change “in the pipeline” without any further increase of atmospheric greenhouse gases (GHGs). That does not mean the problem is unsolvable, but it does mean that we will need to decrease the amount of GHGs in the relatively near future.

The ponderous response of the climate system also means that we don’t need to instantaneously reduce GHG amounts. However, despite uncertainties about some climate processes, we know enough to say that the time scale on which we must begin to reduce atmospheric GHG amounts is measured in decades, not centuries. Given the fact that the fastest time scale to replace energy systems is decades, that means that we must get the political processes moving now. And that won’t happen until the public has understanding of what is actually needed and demands it.

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Previous posts on the climate science and climate policy views of James Hansen can be found here.