American Forests President and CEO Jad Daley issued the following statement in response to the $32 million increase in federal funding for the Urban and Community Forestry (U&CF) Program. The increase is in the FY 2020 Appropriations legislation that was sent to President Donald Trump December 19, 2019 to be signed into law.
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Senior Manager of Communications, Community ReleafJob SummaryThe Senior Manager of Communications leads the development and implementation of all communications strategies for Community ReLeaf, the American Forests program that focuses on planting trees in cities. The strategies are designed to help the organization reach its programmatic and fundraising goals.The position is based
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Senior Manager of Communications, American Releaf Job Summary The Senior Manager of Communications leads the development and implementation of all communications strategies for American ReLeaf, the American Forests program that focuses on restoring forests in large, rural landscapes. The strategies are designed to help the organization reach its programmatic and
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Another year, another AGU. Back in San Francisco for the first time in 3 years, and with a massive assortment of talks, events and workshops. For those not able to go, there is an increasing, though not yet exhaustive, availability of streaming and online content.
Notably, the AGU GO service is streaming 15 sessions live on Wednesday, Thursday and Friday, with the ability to ask questions and interact with other registrants, both in San Francisco and online.
Additionally, there are many posters available electronically at the ‘eLightning’ sessions covering the full range of AGU topics.
The hashtag to follow on Twitter is #AGU19.
Open thread for climate solution discussion. Climate science discussions should remain on the Unforced Variations thread.
A new paper from Hausfather and colleagues (incl. me) has just been published with the most comprehensive assessment of climate model projections since the 1970s. Bottom line? Once you correct for small errors in the projected forcings, they did remarkably well.
Climate models are a core part of our understanding of our future climate. They also have been frequently attacked by those dismissive of climate change, who argue that since climate models are inevitably approximations they have no predictive power, or indeed, that they aren’t even scientific.
In an upcoming paper in Geophysical Research Letters, Zeke Hausfather, Henri Drake, Tristan Abbott and I took a look at how well climate models have actually been able to accurately project warming in the years after they were published. This is an extension of the comparisons we have been making on RealClimate for many years, but with a broader scope and a deeper analysis. We gathered all the climate models published between 1970 and the mid-2000s that gave projections of both future warming and future concentrations of CO2 and other climate forcings – from Manabe (1970) and Mitchell (1970) through to CMIP3 in IPCC 2007.
We found that climate models – even those published back in the 1970s – did remarkably well, with 14 out of the 17 projections statistically indistinguishable from what actually occurred.
We evaluated these models both on how well modeled warming compared with observed warming after models were published, and how well the relationship between warming and CO2 (and other climate forcings) in models compares to observations (the implied transient climate response) (see Figure). The second approach is important because even if an old model had gotten all the physics right, the future projected warming would be off if they assumed we would have 450 ppm CO2 in 2020 (which some did!). Future emissions depend on human societal behavior, not physical systems, and we can usefully distinguish evaluation of climate models physics from paths of future concentrations.
However, it is not totally obvious how one should correct for the forcing assumptions because of subtle issues related to the different efficacy of different forcings and, of course, the remaining uncertainty in the real value of the actual forcings (driven predominantly by the aerosol component). For forcing projections that were close to linear, this didn’t make that much difference, but for scenarios that weren’t (notably scenario C in Hansen et al (1988)), the correction does not work well.
There are a few other results that stand out, notably the (infamous?) low sensitivity result in Rasool and Schneider (1971), which was mainly due to a lack of stratospheric adjustment and water vapor short wave absorption in their formulation. This was noted by Schneider (1975) and the calculation redone by Schneider and Thompson (1981) which turned out to be far more accurate. On the other hand, only Mitchell (1970) appears to have substantially overestimated the TCR – even while he predicted the temperature rise quite accurately (due to a compensation between a too large sensitivity and an underestimate of the forcings). [Amusing aside, both Manabe’s and Mitchell’s 1970 projections appeared in a special volume on the Global Effects of Environmental Pollution, reporting on an 1968 AAAS workshop and edited by (the now-notorious) S. Fred Singer before he went off the deep end].
It’s worth noting that this comparison includes two kinds of climate model – those published prior to 1988 which are energy balance models of varying complexity, and those published afterwards which are true GCMs and include atmospheric (and eventually, ocean) dynamics. Of the early models, the work of Sawyer (1972) stands out as being the most accurate in terms of both temperature trends and forcings, though this must be considered somewhat fortuitous.
The fact that both classes of climate model did so well in projecting future warming should increase our confidence that current climate models are getting things right for mostly the right reasons. While there are still real uncertainties in future warming associated with climate sensitivity, we can confidently state that the rate of surface warming we are experiencing today is pretty much what past climate models projected it would be.
Gosh, maybe we know something about climate after all!
Note: all the data and code for this study are available here.
This month’s open thread. December already?
American Forests has endeavored to lead the way in fostering healthy, resilient forests in the U.S. To further this core mission, we have set a new goal: 3 billion trees planted by 2030. But this is not something we can do without your support. Now through Giving Tuesday – December 3rd – we
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American Forests National Tree Register, Species: Green Ash (Fraxinus pennsylvanica), State: OHDescription Tree is a single stem in good health. The tree has been treated for EAB and the owner is going to continue with the treatments. Location Hocking, OH
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American Forests National Tree Register, Species: Pacific Madrone (Arbutus menziesii), State: CADescription An Abney level from 174 feet horizontal distance corrected for slope was used for measuring the height. 3 separate measurements were made over a 2 hour period by Richard Benjamin, a retired USFS career forester. Measurements were in accord with the measuring Guide
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