Don't Be Distracted by the Latest Tussle Between Mainstreamers and Edge Pushers in Climate Science and Policy

Jim Hansen is roiling climate change science discourse again with a stark warning. Others (including me) say reality is bad enough.

Nov 02, 2023

It’s a busy week on the climate change / crisis / emergency beat.

The dangerously growing “adaptation gap”

First, make sure to read and share the United Nations Environment Programme’s latest Adaptation Gap report - an annual assessment, ahead of each round of climate treaty negotiations, of nations’ investments in work to cut vulnerability to climate hazards. It’s not good news:

Progress on climate adaptation is slowing on all fronts when it should be accelerating to catch up with rising climate change impacts and risks….
Released ahead of the COP28 climate talks taking place in Dubai, United Arab Emirates, the Adaptation Gap Report 2023: Underfinanced. Underprepared – Inadequate investment and planning on climate adaptation leaves world exposed finds that the adaptation finance needs of developing countries are 10-18 times as big as international public finance flows – over 50 per cent higher than the previous range estimate.

To repeat, the financial need is 10 to 18 times as big as existing flows of international public finance. I’ve written since 2002 on the adaptation side of the climate challenge and I recommend you look at my most recent posts here (responding to

Andrew Dessler

) and here: As Harms Mount, U.N. Climate Panel Says Nations Must Boost Resilience of Vulnerable Communities Even as They Cut Heating Gases.

Heat around a stark new climate paper

On the atmosphere end of things, there’s a hot new peer-reviewed paper positing that the climate system is much more sensitive to the jolt of greenhouse gases being added by humans than the gold-standard IPCC assessment has found and that accelerated heating is inevitable without dramatic interventions (more on those in a second).

The 30,000-word (!) paper, led by global warming science pioneer James E. Hansen, was peer reviewed but published in a lower-tier journal. The long list of co-authors includes many longtime colleagues of Hansen and Leon Simons, an independent scholar who has swiftly become a high-profile presence on X and other social media for his focus on cuts in shipping pollution as an explanation for sharp recent heating (a much-debated conclusion).

The new paper is a sprawling multi-disciplinary mashup making some important points - on high odds that accelerated warming is here and the importance of better assessing the impact of sun-shading aerosol pollution along with heat-trapping gases.

Here’s a key excerpt:

[U]nder the present geopolitical approach to GHG [greenhouse gas] emissions, global warming will exceed 1.5°C in the 2020s and 2°C before 2050. [Those are the danger levels negotiated under the Paris Agreement.] Impacts on people and nature will accelerate as global warming increases hydrologic (weather) extremes. The enormity of consequences demands a return to Holocene-level global temperature. Required actions include: (1) a global increasing price on GHG emissions accompanied by development of abundant, affordable, dispatchable clean energy, (2) East-West cooperation in a way that accommodates developing world needs, and (3) intervention with Earth’s radiation imbalance to phase down today’s massive human-made ‘geo-transformation’ of Earth’s climate. Current political crises present an opportunity for reset, especially if young people can grasp their situation.

But as you can see the paper also blends in policy prescriptions that Hansen has long favored - a rising global fee on greenhouse gas emissions (that would conflict with his call for equity for developing countries) and a call for active geoengineering work to reflect some sunlight to counter greenhouse heating.

It’s tough to pull off mixing the “is” of science and “ought” of policy, as the philosopher David Hume long ago warned.

read my post about the “is/ought problem” in the climate debate

A heap of established climate researchers are not-so-gently pushing back on the paper’s core conclusions. A good start is Michael E. Mann’s long, respectful, but tough critique on his website. Here’s his closing point but do read the piece:

[While] I hold James Hansen to be one of the most (if not the most) important contributors to our modern scientific understanding of human-caused climate change, I feel that this latest contribution from Jim and his co-authors is at best unconvincing. I don’t think they have made the case for their main claims, i.e. that warming is accelerating, that the planetary heat imbalance is increasing, that aerosols are playing some outsized role, or that climate models are getting all of this wrong. And I certainly don't think that they've made the case for engaging in potentially disastrous planetary-scale geoengineering projects.

Hansen et al’s dramatic conclusions, combined with methodological weak spots identified by by other scientists, mean readers are being buffeted with stark Guardian-style climate emergency headlines and coverage and other output saying not so fast.

This is the “whiplash effect” I’ve warned about since 2008.

Warning, single-study syndrome

How do you ride it out? Keep in mind my other longstanding recommendation to avoid “single-study syndrome” - paying outsize attention to dramatic findings on science frontiers. They may indeed end up right, but often don’t. I have warning labels for both whiplash and single studies. Feel free to use them!

“1.5 is deader than a doornail”

In an online press briefing today, Hansen did offer some personal observations that mesh with my view based on 35 years of reporting on his work, the IPCC and both basic climate science and energy realities. Here’s a snippet of video from my livestream of part of the press briefing (the full video is below):

Jim Hansen:

“1.5 is deader than a doornail. And anybody who understands the physics knows that. And when you look at the real potential, if you look at the energy story, you will understand that the rest of the world is not going to suddenly get off of fossil fuels. They're just too convenient. They raise standards of living. As I've said a number of times, one gallon of gasoline contains more than 400 hours of labor by a healthy adult. As I showed in a graph on the carbon intensity of energy we use, we reduced it from .8 to .7 in 50 years. It's not going to go to zero in a few decades. And there are no plans to do that.

I agree with him on this but see that reality less a reason for panic as a reason to deeply question the decades-long effort to draw lines in the sand like 1.5 or 2 degrees C. Rising emissions and temperatures = rising risk (even with adaptation efforts). Change those curves by all means possible.

Here’s the full briefing video on the new paper from the U.N. Sustainable Development Solutions Network:

The sun-shading solution (added 11/3/23)

I just edited a small clip from the briefing video in which Jim Hansen explains why he sees no way to avoid blunting what he describes as the unintentional geoengineering that’s under way right now through the human-driven CO2 buildup with intentional geoengineering aimed at reducing incoming solar radiation. I think his stance, a stark contrast with some of his peers in climate science, illustrates how there will always be “response diversity” in human communities to a stress like climate change.

Here’s a transciption of Hansen’s solar geoengineering remarks:

Jim Hansen: Well we we're going to have to reduce emissions as rapidly as practicable because otherwise any artificial ways to cool the planet are going to be overwhelmed. But we know when [Mount] Pinatubo went off, it put aerosols in the stratosphere which changed the planet's energy budget by three watts per meter squared reduction. If you had that now, that's more than enough to put you from warming into cooling. So there are there are ways to do it and not just putting aerosols in the stratosphere there. You can have autonomous sailboats putting sea salt in the atmosphere and seeding clouds, which many people would consider more innocuous than putting aerosols in the stratosphere.
But rather than describe those efforts and as threatening geoengineering, we have to recognize we're geoengineering the planet right now. What we're doing with these huge greenhouse gas amounts in the atmosphere is forcing the planet at a rate ten times greater than has ever occurred in the Earth's history, as far as we know. We have to minimize that human-made geoengineering and on a temporary timescale that will probably require reflecting sunlight just because of how difficult it is to get the greenhouse gases out of the atmosphere.
We're not going to do such a thing this year or next year. People have to understand the situation. They have to see that the problem is getting worse and worse and and we have to understand the implications better…. We have to compare the current geoengineering, with the strong warming that that causes and all the problems that's going to cause at low latitudes and increased storms and increased floods and things with the situation where we bring the temperature back down. It may have regional effects, but overall the global climate effects are likely, are surely, much less than if we continue on this path and get several degrees of global warming.

This video from the Great Barrier Reef Foundation describes an example of the kind of low-level solar radiation management through “marine cloud brightening” that Hansen is talking about:

I’ll devote more space here to geoengineering in the months ahead.

Finally,