XPost: alt.deadmolly.woodchipper, alt.fan.rush-limbaugh, alt.global-warming XPost: talk.politics.guns

Molly Bolt <mollythebolt666@gmail.com> wrote in news:3d92e691-b71b-4d50-9deb-bd4f455b2c27n@googlegroups.com:

Someday I hope I don't have to live in my parent's basement. But I am
gay and have no real job skills so my options are limited. Especially
since I got the picture of Obama's ass tattooed on my face.

Recent climate models project that a doubling of atmospheric CO2 above pre-industrial levels could cause temperatures to soar far above previous estimates. A warming earth, researchers now say, will lead to a loss of
clouds, allowing more solar energy to strike the planet.

It is the most worrying development in the science of climate change for a
long time. An apparently settled conclusion about how sensitive the
climate is to adding more greenhouse gases has been thrown into doubt by a series of new studies from the world’s top climate modeling groups.

The studies have changed how the models treat clouds, following new field research. They suggest that the ability of clouds to keep us cool could be drastically reduced as the world warms — pushing global heating into
overdrive.

Clouds have long been the biggest uncertainty in climate calculations.
They can both shade the Earth and trap heat. Which effect dominates
depends on how reflective they are, how high they are, and whether it is
day or night. Things are made more complicated because cloud dynamics are complex and happen on small scales that are hard to include in the models
used to predict future climate.

Recent concern about how accurately the models handle clouds has focused
on the blankets of low clouds that any international flyer will have seen extending for hundreds of miles below them across the oceans. Marine
stratus and stratocumulus clouds predominantly cool the Earth. They shade roughly a fifth of the oceans, reflecting 30 to 60 percent of the solar radiation that hits them back into space. In this way, they are reckoned
to cut the amount of energy reaching the Earth’s surface by between 4 and
7 percent.

But it seems increasingly likely that they could become thinner or burn
off entirely in a warmer world, leaving more clear skies through which the
sun may add a degree Celsius or more to global warming. As Mark Zelinka of
the Lawrence Livermore National Laboratory, lead author of a review of the
new models published last month, has put it: The models “are shedding
their protective sunscreen in dramatic fashion.”

The debate about clouds and climate change is part of a larger concern
about feedbacks in warming the world.
The new predictions overturn a consensus about the planet’s climate
sensitivity that has persisted for the entire 32-year history of the UN’s Intergovernmental Panel on Climate Change. All five of the IPCC’s
scientific assessments have agreed that doubling carbon dioxide, the most critical planet-warming greenhouse gas, from pre-industrial levels will eventually warm us by about 3 degrees C (5.4 degrees F), with an error bar extending from a low of 1.5 degrees C (2.7 degrees F) to a high of 4.5
degrees C (8 degrees F). This is known in the jargon as the equilibrium
climate sensitivity.

That consensus was reaffirmed in 2018 when a widely cited review, headed
by Peter Cox of the University of Exeter, found that the chance of climate sensitivity exceeding 4.5 degrees was “less than 1 percent.”

But the consensus has now been blown apart. Most leading climate models — including those from the U.S. National Center for Atmospheric Research
(NCAR) and Britain’s Hadley Center — are now calculating the climate’s sensitivity to doubling CO2 levels as a degree or more higher, ranging up
to 5.6 degrees C (10 degrees F). Their findings are almost certain to
feature strongly in the next IPCC assessment of the physical science of
climate change, due to be signed off in April next year.

In the meantime, the new findings should make disturbing reading for
climate negotiators preparing a new deal on reducing greenhouse-gas
emissions to be agreed in Glasgow, Scotland, this November. That’s because
the revised estimates make the prospect of keeping global warming below 2 degrees C — let alone the aspiration of 1.5 degrees C agreed in the Paris climate accord five years ago — even more unlikely.

The debate about the role of clouds in climate change is part of a larger concern about feedbacks in warming the world. It has long been clear that
the “greenhouse effect” of doubling CO2 in the atmosphere will directly
raise global temperatures by about 1 degree C. The physics of that is undisputed. But that is only the beginning. Things get more complicated —
and concerning — because of amplifying feedbacks caused by how natural
systems respond to this initial warming. None are easy to assess
accurately.

One feedback is the melting of the ice and snow that covers large areas of
the planet. This replaces light-reflective surfaces with darker land and
ocean that absorb solar energy and then radiate it, heating the air. It
remains far from clear how fast sea ice, in particular in the Arctic
Ocean, will disappear. The trend, however, has been alarming, with Arctic
sea ice extent shrinking by about 10 percent per decade over the last 40
years.

A second is the additional water vapor likely in a future atmosphere as
higher temperatures cause more evaporation from land and ocean. Water
vapor is an important greenhouse gas in its own right. Climate models
estimate that the extra water vapor will at least double the direct
greenhouse effect.

The third feedback, and the most uncertain, is clouds. A lot of the water
vapor in the air forms water droplets that coalesce into clouds. We
generally think of clouds as keeping us cool, and more water vapor should
make more clouds. That may sound helpful. But things are not so simple.

While during the day, low clouds shade the planet, at night they act as an insulating blanket. Meanwhile high cirrus clouds predominantly act as heat traps, warming the air below them. Generally, at a global level, models
have suggested that the warming and cooling effects cancel each other out,
and the presumption has been that that will continue as the world warms.
But the new model analyses suggest otherwise.

At a meeting in Barcelona last March, climate modelers first began to
realize that most of the world’s leading climate models were rejecting the
old IPCC consensus. The data is now increasingly becoming public. First,
in July, Andrew Gettelman at NCAR reported that the center’s revised
modeling came up with a climate sensitivity — the temperature increase
based on a projected doubling of CO2 levels — of 5.3 degrees C (9.5
degrees F), a 32 percent increase over its previous estimate of 4 degrees
C.

Clouds would thin out and many would not form at all, resulting in extra warming.
Others soon followed. Last month, American and British researchers, led by Zelinka, reported that 10 of 27 models they had surveyed now reckoned
warming from doubling CO2 could exceed 4.5 degrees C, with some showing
results up to 5.6 degrees. The average warming projected by the suite of
models was 3.9 degrees C (7 degrees F), a 30-percent increase on the old
IPCC consensus.

French scientists at the National Center for Scientific Research concluded
that the new models predicted that rapid economic growth driven by fossil
fuels would deliver temperature rises averaging 6 to 7 degrees C (10.8 to
12.6 degrees F) by the end of the century. They warned that keeping
warming below 2 degrees C was all but impossible.

Zelinka said the new estimates of higher climate sensitivity were
primarily due to changes made to how the models handled cloud dynamics.
The models found that in a warmer world clouds would contain less water
than previously thought. Clouds would thin out, and many would not form at
all, resulting in “stronger positive cloud feedbacks” and extra warming.

This tweaking of the models followed recent field research over the
Southern Ocean, which is currently one of the cloudiest regions on Earth. Flying through those clouds, researchers found they contain much more
water and less ice than previously assumed. They were “optically thicker
and hence more reflective of sunlight,” says NASA’s Ivy Tan.

That sounds like good news. But it means that past models have
overestimated how much ice in these clouds will turn to liquid water in a warmer world — and so overestimated both the thickness of future clouds
and their ability to keep us cool. Eliminating that bias, says Tan, could increase climate sensitivity by as much as 1.3 degrees C.

Real-world data from satellites suggests that the modelers’ predictions
may already be coming true.
Modelers have also changed how they characterize the effect of
anthropogenic aerosols from burning fuel, particularly in clouds. In
general, the aerosols make clouds thicker and better able to shade the
planet. The recent recalculation follows new estimates of aerosol
emissions during the mid-20th century, a time when booming emissions from
rapid industrialization caused the planet to cool for several decades,
masking the warming effect of accumulating CO2.

Researchers have concluded from the new data that both the cooling effect
of aerosols and the warming effect of CO2 have been greater than
previously supposed, causing them to revise upward their estimates of the climate’s sensitivity to CO2. With CO2 continuing to accumulate and
stricter controls on smog, the masking effect of particulate aerosols is
bound to diminish in the future. So the increased climate sensitivity to
CO2 is set to dominate, giving an extra kick to warming.

Real-world data from satellites suggests that the modelers’ predictions
may already be coming true. Norman Loeb of NASA’s Langley Research Center
has shown that a sharp rise in global average temperatures since 2013 has coincided with a decline in cloud cover over the oceans. He argues that
the clearer skies may have resulted from stricter pollution controls in
China and North America.

Other researchers have reported fewer low-level clouds in the tropics
during warmer years. In his 2016 study, climate scientist Tapio Schneider,
then at ETH Zurich, noted that climate models that incorporated this link
in their calculations predicted faster global warming.

Schneider, now at Caltech, made waves last February by arguing that global cloud cover may have a tipping point, beyond which clouds would “become unstable and break up,” sending warming into an upward spiral. He used a
model with a fine-scale resolution that, he said, represented the real
dynamics of clouds much better than the models used to calculate climate change.

The tipping point would not be reached until CO2 levels were at around
1200 ppm, more than four times pre-industrial levels, and three times
current levels. But once it was passed, he projected that temperatures
would soar by an additional 8 degrees C (14.4 degrees F) as a result of
the lost clouds. He suggested that such a tipping point “may have
contributed importantly to abrupt climate changes in the geological past.”

This is not the first time that such scary climate predictions have
emerged from modeling analysis of how clouds might change in a warmer
world. Fifteen years ago, I attended a workshop of climate modelers where
James Murphy of Britain’s Hadley Centre discussed how he had tweaked his center’s standard climate model to reflect more fully the uncertainty
about cloud cover, cloud duration, and thickness. The resulting graph
showed the most likely warming still at 3 degrees C or so, but with a
“long tail” at the top end. There was a possibility — he put it no higher
— that warming could go as high as 10 degrees C (18 degrees F) for
doubling CO2.

David Stainforth of Oxford University had done the same thing on another
model and saw a “long tail” extending to 12 degrees C. They both later published their findings in Nature, but the findings were subsequently
rather sidelined by modelers. They did not make it into summaries of IPCC climate science assessments. But the new, hotter projections emerging from
the latest mainstream model runs suggest that Murphy and Stainforth were
onto something.

<https://e360.yale.edu/features/why-clouds-are-the-key-to-new-troubling- projections-on-warming>

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