It would be good news if the climate’s sensitivity to carbon pollution were on the low side. No, that wouldn’t save us from catastrophic global warming — 7°F warming or higher — if we stay anywhere near our current emissions path (as I explain in “Error-Riddled Matt Ridley Piece…”).
But a low sensitivity would mean that aggressive action to reduce CO2 emissions starting now would have a modestly higher chance of keeping total warming below 4°F and averting the worst impacts. That’s the point of New Scientist‘s article, “A second chance to save the climate” on a new sensitivity study in Nature Geoscience:
“If we are lucky and the climate sensitivity is at the low end, and we have a strong agreement in 2015, then I think we stand a chance to limit climate change to 2 °C,” says Corinne Le Quéré of the Tyndall Centre for Climate Change Research in Norwich, UK. “But there’s a lot of ifs.”
If this new study is accurate, then near-term surface warming might be less than expected. But as the lead author Oxford’s Dr. Alexander Otto told the BBC “We would all like climate sensitivity to be lower but it isn’t.”
The researchers say the difference between the lower short-term estimate and the more consistent long-term picture can be explained by the fact that the heat from the last decade has been absorbed into and is being stored by the world’s oceans.
Recent studies make clear the ocean is warming quite fast, as “In Hot Water: Global Warming Has Accelerated In Past 15 Years, New StudyOf Oceans Confirms” and “New Study: When You Account For The Oceans, Global Warming Continues Apace.” If, as many climatologists believe, some of that ocean heat is released to the surface in the next decade or two, that would reverse the recent slowdown in the rate of surface warming.
Also, many other recent studies find that the climate is more sensitive than we expected:
Indeed, the new study does little to eliminate the confusion about sensitivity. The media continue to conflate and confuse climate sensitivity with how much warming will we subject our children and countless future generations to (see below).
Another related source of confusion is conflating “climate sensitivity” — which generally refers to the change in the global surface temperatures (absent major feedbacks) — with how sensitive the climate itself is to changes in temperature.
Arctic sea ice is melting much, much faster than even the best climate models had projected (actual observations in red). The reason is most likely unmodeled amplifying feedbacks. The image (from Climate Crocks via Arctic Sea Ice Blog) comes from a 2007 GRL research paper by Stroeve et al.
And considerable recent research suggests that our climate in turn is much more sensitive to Arctic ice loss than we ever thought:
- “Arctic Warming Favors Extreme, Prolonged Weather Events ‘Such As Drought, Flooding, Cold Spells And Heat Waves’”
Finally, since the media keep misreporting the issue, here once again are the four factors that determine how much warming we are going to inflict on future generations:
1. The so-called “equilibrium climate sensitivity” – the sensitivity of the climate to fast feedbacks like sea ice and water vapor. The ECS, which is typically the focus of modeling studies like the new one discussed above, is how much warming you get if we suddenly adopt a super-aggressive effort to cut carbon pollution and only double CO2 emissions to 560 ppm — and there are no major “slow” feedbacks. We know the fast feedbacks, like water vapor, are strong by themselves (see “Study: Water-vapor feedback is “strong and positive,” so we face “warming of several degrees Celsius” and Skeptical Science piece).
2. The actual CO2 concentration level we hit, which on our current emissions path is far, far beyond 550 ppm (see “U.S. media largely ignores latest warning from climate scientists: “Recent observations confirm … the worst-case IPCC scenario trajectories are being realised” — 1000 ppm”).
3. The real-world slower (decade-scale) feedbacks, such as tundra melt (see “Carbon Feedback From Thawing Permafrost Will Likely Add 0.4°F – 1.5°F To Total Global Warming By 2100“).
4. Where they live — since people who live in the mid-latitudes (like most Americans) are projected to warm considerably more than the global average.
The Intergovernmental Panel on Climate Change concluded in 2007 that equilibrium climate sensitivity was in the range of 2.0-4.5C. The new study has a similar range, 0.9-5.0C.
Actual warming this century on our current emissions path is all but certain to be catastrophic, even if ECS is closer to 2°C than 3°C or more.
Michael Marshall, “A second chance to save the climate,” New Scientist (May 19, 2013). www.newscientist.com/article/dn23565-a-second-chance-to-save-the-climate.html?cmpid=RSS|NSNS|2012-GLOBAL|climate-change
Matt McGrath, “Climate slowdown means extreme rates of warming ‘not as likely’,” BBC (May 19, 2013). www.bbc.co.uk/news/science-environment-22567023
Dana Nuccitelli via Skeptical Science, “In Hot Water: Global Warming Has Accelerated In Past 15 Years, New Study Of Oceans Confirms,” Think Progress (March 25, 2013). thinkprogress.org/climate/2013/03/25/1768601/in-hot-water-global-warming-has-accelerated-in-past-15-years-new-study-of-oceans-confirms/
Joe Romm, “Error-Riddled Matt Ridley Piece Lowballs Climate Change, Discredits Wall Street Journal. World Faces 10°F Warming,” Climate Progress (Dec. 20, 2012).thinkprogress.org/climate/2012/12/20/1365671/error-riddled-matt-ridley-piece-lowballs-global-warming-discredits-wall-street-journal-world-faces-10f-warming/
Joe Romm, “New Study: When You Account For The Oceans, Global Warming Continues Apace,” Climate Progress (May 12, 2013). thinkprogress.org/climate/2013/04/08/1836231/new-study-when-you-account-for-the-oceans-global-warming-continues-apace/?mobile=nc
Joe Romm, “Climate Sensitivity Stunner: Last Time CO2 Levels Hit 400 Parts Per Million The Arctic Was 14°F Warmer!,” Think Progress (May 12, 2013). thinkprogress.org/climate/2013/05/12/1993531/climate-sensitivity-stunner-last-time-co2-levels-hit-400-parts-per-million-the-arctic-was-14f-warmer/
Joe Romm, “Science Stunner: Observations Support Predictions Of Extreme Warming And Worse Droughts This Century,” Climate Progress (November 9, 2012). thinkprogress.org/climate/2012/11/09/1170701/science-stunner-observations-support-predictions-of-extreme-warming-worse-droughts-this-century/
Andrew Freedman, “Arctic Warming Favors Extreme, Prolonged Weather Events ‘Such As Drought, Flooding, Cold Spells And Heat Waves’,” Climate Progress (Apr 4, 2012), reposted from Climate Central. thinkprogress.org/climate/2012/04/04/457823/arctic-warming-extreme-weather-events-drought-flooding-cold-spells-and-heat-waves/
Joe Romm, “NOAA Bombshell: Warming-Driven Arctic Ice Loss Is Boosting Chance of Extreme U.S. Weather,” Climate Progress (Oct. 11. 2013). thinkprogress.org/climate/2012/10/11/989231/noaa-bombshell-warming-driven-arctic-ice-loss-is-boosting-chance-of-extreme-us-weather/
Joe Romm, “How Arctic Ice Loss Amplified Superstorm Sandy — Oceanography Journal,” Climate Progress (Mar. 15, 2013). thinkprogress.org/climate/2013/03/15/1725461/how-arctic-ice-loss-amplified-superstorm-sandy-oceanography-journal/
Joe Romm, “Study: Water-vapor feedback is “strong and positive,” so we face “warming of several degrees Celsius”, Climate Progress (Oct. 26, 2008). thinkprogress.org/climate/2008/10/26/203243/study-water-vapor-feedback-is-strong-and-positive-so-we-face-warming-of-several-degrees-celsius/
Joe Romm, A detailed look at climate sensitivity, via Skeptical Science in Climate Progress (Sept. 19, 2010). thinkprogress.org/climate/2010/09/19/206503/climate-sensitivity-lukewarmers/
Joe Romm, “U.S. media largely ignores latest warning from climate scientists: “Recent observations confirm … the worst-case IPCC scenario trajectories (or even worse) are being realised” — 1000 ppm,” Climate Progress (Mar. 17, 2009). thinkprogress.org/climate/2009/03/17/203822/media-copenhagen-global-warming-impacts-worst-case-ipcc/
Andy Skuce, “Carbon Feedback From Thawing Permafrost Will Likely Add 0.4°F – 1.5°F To Total Global Warming By 2100” Climate Progress via Skeptical Science (Oct. 6, 2012). thinkprogress.org/climate/2012/10/06/970721/carbon-feedback-from-thawing-permafrost-will-add-04f-15f-to-total-global-warming-by-2100/
This Commentary was originally published on Climate Progress (May 13, 2013).
Joe Romm is a Fellow at American Progress and is the editor of Climate Progress, which New York Times columnist Tom Friedman called “the indispensable blog” and Time magazine named one of the 25 “Best Blogs of 2010.” In 2009, Rolling Stone put Romm #88 on its list of 100 “people who are reinventing America.” Time named him a “Hero of the Environment″ and “The Web’s most influential climate-change blogger.” Romm was acting assistant secretary of energy for energy efficiency and renewable energy in 1997, where he oversaw $1 billion in R&D, demonstration, and deployment of low-carbon technology. He is a Senior Fellow at American Progress and holds a Ph.D. in physics from MIT.
- “Memo To Media: ‘Climate Sensitivity’ Is NOT The Same As Projected Future Warming, World Faces 10°F Rise” thinkprogress.org/climate/2013/02/04/1507261/memo-to-media-climate-sensitivity-is-not-the-same-as-projected-future-warming-world-faces-10f-rise/