While this is not holiday cheer, I thought everyone should know about the following recent climate change research.
This is an important paper that makes a number of key points, but the bottom line is we must act immediately to address the climate crisis. Hansen uses the framing "human-made geoengineering of Earth’s climate must be rapidly phased out” to call for emissions elimination, Carbon Dioxide Removal (CDR) and Solar Radiation Management (SRM).
Hansen Newsletter Summary:
Full paper PDF:
Here is a summary of some of the key points of this quite long (48 page) paper:
1. The Earth Climate Sensitivity (ECS) — the Earth’s short-term response to a CO2 doubling — is higher than previously assumed. Most scientists said it was ~3ºC, but Hansen et al now say it is 4ºC or more based on paleoclimate data. This means there is more warming “in the pipeline” than previously assumed.
2. While humans have increased atmospheric CO2 by 50% since the industrial revolution, the actual climate forcing from all the added greenhouse gases is now ~4W/m^2, which is equivalent to a doubling of CO2 (i.e., CO2e (including all greenhouse gases, not just CO2) is about 560 ppm).
3. Part of the current warming has been hidden by human-made particulate air pollution (aerosols), mainly sulfur. When North America and Europe started to reduce emissions after the introduction of clean air acts in the 1970's, regional and global warming became more pronounced. In the past decades China and global shipping slashed sulfur emissions through cleaner fuels and sulfur filter systems ('scrubbers'). There are clear signals from ground, ocean and satellite based observations that the rate of global warming has recently doubled, which needs to be taken into account in risk assessments.
4. Assuming today’s forcing (4 W/m^2) stabilizes and human-made aerosols are eliminated, when all feedbacks — including “long-term” feedbacks — play out, we are on track for about 10ºC warming and 6~7ºC if aerosols stay at today’s levels. This is a “scenario” and we still control our future, though we are on track to increase climate forcing from today’s 4 W/m^2.
5. If greenhouse gas forcing keeps growing at the current rate, it could match the level of the PETM mass extinction within a century
. We are increasing climate forcing 20X faster than in the PETM so “long-term” feedbacks won’t take as long as in the paleo record (though some feedbacks will still be much longer than a human lifetime).
6. The paper concludes that we must: (a) implement a carbon fee and border duty (Fee and Dividend
); (b) "human-made geoengineering of Earth’s climate must be rapidly phased out,”
i.e., we must stop emitting greenhouse gases, remove CO2 from the atmosphere, and research and implement safe solar radiation management to counter the massive geoengineering experiment we are currently running; and (c) we must improve international cooperation to allow the developing world to grow using clean energy.
7. A companion paper will be coming out that addresses the near-term shutdown of the AMOC and associated “multi-meter” sea level rise on a century timescale.
I did a (2.5 hour) Clubhouse room on this subject recently with Leon Simons, one of the co-authors of the paper. You can listen to the discussion in your browser.
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