[MCN] We're still moving right along to too hot for farm/food, forest, and the terrestrial carbon sink.

[Lance Olsen]

First, whether now or later, be sure to check out this excellent, thoughtful reporting on efforts to keep Earth heat from rising to catastrophic levels. As usual, Vox’s David Roberts does an unparalleled job that deserves the widest possible circulation:
<<https://www.vox.com/energy-and-environment/21396261/senate-climate-change-committee-report-brian-schatz-koch-industries <https://www.vox.com/energy-and-environment/21396261/senate-climate-change-committee-report-brian-schatz-koch-industries>>>

That said, the trends don’t look cheerful even short of catastrophe, beginning with these 3 reports on on recent analysis
 <https://www.carbonbrief.org/climate-change-could-cut-growing-days-of-plants-and-crops-by-11>
Climate change could cut growing days of plants and crops by ... <https://www.carbonbrief.org/climate-change-could-cut-growing-days-of-plants-and-crops-by-11>
Jun 11, 2015 - And if emissions remain unchecked,... rising temperatures could make conditions too hot for plant growth.
 <https://grist.org/science/think-climate-change-will-be-good-for-plants-think-again/>
Think climate change will be good for plants? Think again | Grist <https://grist.org/science/think-climate-change-will-be-good-for-plants-think-again/>
Jun 12, 2015 - Why did Mora decide to study changes in growing seasons? ... In the tropics temperatures got too hot for numerous plants and drought rose, ...
 <https://time.com/3916200/climate-change-plant-growth/>
Effects of Climate Change: Rising Temperatures Harm Plant ... <https://time.com/3916200/climate-change-plant-growth/>
time.com › Science › climate change <https://time.com/3916200/climate-change-plant-growth/>
Jun 11, 2015 - Overall, climate change is expected to stunt plant growth.

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"In temperate regions, the hottest seasons on record will represent the future norm in many locations.
 
“Coping with the short-run challenge of food price volatility is daunting. But the longer-term challenge of avoiding a perpetual food crisis under conditions of global warming is far more serious. “
 
David. S. Battisti  and Rosamond L. Naylor.
Historical Warnings of Future Food Insecurity with Unprecedented Seasonal Heat. Science  09 Jan 2009

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“ … we expect with high confidence that global-average temperatures greater than those observed in 2015 will occur at least every second year by 2040.” 

Sophie C. Lewis et al. DEFINING A NEW NORMAL FOR EXTREMES IN A WARMING WORLD
Bulletin of the American Meteorological Society, June 2017

Open access:
<<https://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-16-0183.1>>

==================================

“Droughts of the twenty-first century are characterized by hotter temperatures, longer duration, and greater spatial extent …. This situation increases the vulnerability of ecosystems to drought, including a rise in drought-driven tree mortality globally (Allen et al. 2015) and anticipated ecosystem transformations from one state to another—for example, forest to a shrubland (Jiang et al. 2013). When a drought drives changes within ecosystems, there can be a ripple effect through human communities that depend on those ecosystems for critical goods and services (Millar and Stephenson 2015). …. Despite the high costs to both nature and people, current drought research, management, and policy perspectives often fail to evaluate how drought affects ecosystems and the “natural capital” they provide to human communities. Integrating these human and natural dimensions of drought is an essential step toward addressing the rising risk of drought in the twenty-first century. 

Crausbay, et al. Defining Ecological Drought for the Twenty-First Century. Bulletin of the American Meteorological Society. December 2017.

Open Access
<<https://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-16-0292.1>> 

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University of Queensland <http://www.uq.edu.au/> AUGUST 20, 2020
Plants take in less carbon in a warming world
by Dominic Jarvis, University of Queensland <http://www.uq.edu.au/>
<<https://phys.org/news/2020-08-carbon-world.html <https://phys.org/news/2020-08-carbon-world.html>>>

As world temperatures rise, the rate at which plants in certain regions can absorb carbon dioxide is declining, according to University of Queensland research.

Over a three year period, researchers took direct measurements of plant absorption of CO2 in subtropical coastal ecosystems in eastern Australia.
Professor Hamish McGowan, from UQ's School of Earth and Environmental Sciences, said the team found the optimum temperature <https://phys.org/tags/temperature/> for photosynthetic production was routinely exceeded in these regions.

"Plants' optimum temperature range for photosynthesis in our study area is between 24.1 and 27.4 degrees Celsius," Professor McGowan said.

"But due to anthropogenic climate change <https://phys.org/tags/anthropogenic+climate+change/>, temperatures—particularly in warmer months—often go well beyond this 'healthy' range for carbon absorption. It was eye opening—temperatures exceeded this range between 14 and 59.2 percent of the time, depending on which site you were looking at. Plants in these regions simply aren't able to absorb carbon like they used to, which is seriously concerning."

The research team also measured the rate at which photosynthesis was occurring, with alarming results.

"Once this temperature range is exceeded, the ability for plants to appropriate carbon falls off a cliff," Professor McGowan said.

"Sequestering carbon is incredibly important right now—we need to drastically reduce the greenhouses gasses in our atmosphere to maintain a healthy climate for us and future generations <https://phys.org/tags/future+generations/>. We are seeing through observational evidence that a dangerous positive feedback loop is being created, making the world even hotter."

Professor McGowan said the effects of a changing climate on rainfall in subtropical ecosystems were compounding the issue.

"While future warming will cause rainfall in some tropical regions to increase, in the subtropics and Mediterranean climate zones it is likely to decrease," he said.

"This inevitably leads to reduced growth and increased risk of tree mortality, reducing even further these areas' potential to sequester carbon dioxide <https://phys.org/tags/carbon+dioxide/>. Much of the current modeling doesn't capture these nuances—the ongoing sequestered carbon we were counting on in subtropical coastal regions might not come to pass. There's an urgent need to extend our research to other biomes so that the effects of temperature and moisture availability on carbon sequestration by photosynthesis can be quantified. It's critical we have up to date information, temperature predictions and realistic carbon budgets. But most importantly, the world needs an effective global agreement to markedly reduce carbon <https://phys.org/tags/carbon/> emissions to the atmosphere."

More information: Hamish A. McGowan et al. Identification of Optimum Temperatures for Photosynthetic Production in Subtropical Coastal Ecosystems: Implications for CO 2 Sequestration in a Warming World, Journal of Geophysical Research: Biogeosciences (2020). DOI: 10.1029/2020JG005678 <http://dx.doi.org/10.1029/2020JG005678>
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News Release 20-Aug-2020 <https://www.eurekalert.org/pub_releases/2020-08/uob-aci082020.php>
Anthropogenic CO2 increase is unprecedented <https://www.eurekalert.org/pub_releases/2020-08/uob-aci082020.php>
UNIVERSITY OF BERN <https://www.eurekalert.org/pub_releases/2020-08/uob-aci082020.php>
Even in earlier warm periods there were pulse-like releases of CO2 to the atmosphere. Today's anthropogenic CO2 rise, however, is more than six times larger and almost ten times faster than previous jumps in the CO2 concentration.  <https://www.eurekalert.org/pub_releases/2020-08/uob-aci082020.php>
JOURNAL <https://www.eurekalert.org/pub_releases/2020-08/uob-aci082020.php>
Science <https://www.eurekalert.org/pub_releases/2020-08/uob-aci082020.php>

<<https://www.eurekalert.org/pub_releases/2020-08/uob-aci082020.php <https://www.eurekalert.org/pub_releases/2020-08/uob-aci082020.php>>>

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“Scotland can expect more rain, more droughts, more storms, more wild fires, more landslides, more pests and more diseases – and snow is disappearing from the mountains.”
 
<<https://www.heraldscotland.com/news/15497924.revealed-climate-change-and-the-terrifying-risk-to-scotland/ <https://www.heraldscotland.com/news/15497924.revealed-climate-change-and-the-terrifying-risk-to-scotland/>>>


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"The greatest disturbances of which we are aware are those now being introduced by man himself. Since his tampering with the biological and geochemical balances may ultimately prove injurious -- even fatal -- to himself, he must understand them better than today."

Bert Bolin. "The Carbon Cycle."

Scientific American, September 1970

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 Is there really still a chance for staying below 1.5 °C global warming?

Stefan Rahmstorf

"We still live in a world on a path to 3 or 4 °C global warming, waiting to finally turn the tide of rising emissions. At this point, debating whether we have 0.2 °C more or less to go until we reach 1.5 °C is an academic discussion at best, a distraction at worst. The big issue is that we need to see falling emissions globally very very soon if we even want to stay well below 2 °C. That was agreed as the weaker goal in Paris in a consensus by 195 nations. It is high time that everyone backs this up with actions, not just words.”

<<http://www.realclimate.org/index.php/archives/2017/09/is-there-really-still-a-chance-for-staying-below-1-5-c-global-warming/ <http://www.realclimate.org/index.php/archives/2017/09/is-there-really-still-a-chance-for-staying-below-1-5-c-global-warming/>>>

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