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<div><font face="Lucida Grande">SEARING HEAT WAVES DETAILED IN STUDY
OF FUTURE CLIMATE<br>
<u
>https://www2.ucar.edu/atmosnews/news/19559/searing-heat-waves-detaile</u
>d-study-future-climate<br>
February 23, 2016<br>
<br>
Sweltering heat waves that typically strike once every 20 years could
become yearly events across 60 percent of Earth's land surface by
2075, if human-produced greenhouse gas emissions continue
unchecked. <br>
<br>
If stringent emissions-reduction measures are put in place, however,
these extreme heat events could be reduced significantly. Even so, 18
percent of global land areas would still be subjected yearly to these
intense heat waves, defined as three exceptionally hot days in a
row.<br>
<br>
These are among the findings of a new study by Claudia Tebaldi of the
National Center for Atmospheric Research and Michael Wehner of the
Lawrence Berkeley National Laboratory. The study, funded by the U.S.
Department of Energy and published in the journal Climatic Change,
quantifies the benefits society would reap, in terms of avoiding
extreme heat events, if action is taken now to mitigate climate
change.<br>
<br>
"The study shows that aggressive cuts in greenhouse gas emissions
will translate into sizable benefits, starting in the middle of the
century, for both the number and intensity of extreme heat events,"
Tebaldi said. "Even though heat waves are on the rise, we still
have time to avoid a large portion of the impacts."<br>
<br>
<b>MORE FREQUENT, MORE SEVERE</b><br>
Tebaldi and Wehner used data generated by the NCAR-based Community
Earth System Model to study 20-year extreme heat events-those intense
enough to have just a 1-in-20 chance of occurring in any given year.
The model was developed with support from the Department of Energy and
the National Science Foundation, NCAR's sponsor.<br>
<br>
The researchers looked at two things: how frequently today's typical
20-year heat wave may occur in the future, as well as how much more
intense future 20-year heat waves will be.<br>
<br>
Besides finding that today's 20-year heat waves could become annual
occurrences across more than half of the world's land areas by 2075,
the study also concluded that heat waves with a 1-in-20 chance of
occurring during a future year will be much more extreme than heat
waves with the same probability of occurring today.<br>
<br>
For example, if emissions remain unabated, a heat wave with a 1-in-20
chance of occurring in 2050 would be at least 3 degrees Celsius (5.4
degrees Fahrenheit) hotter for 60 percent of the world's land areas.
For 10 percent of land areas, a 20-year heat wave in 2050 would be at
least 5 degrees C (9 degrees F) hotter.<br>
<br>
A few degrees may not seem like much on a mild day, but during extreme
heat events, they can mean the difference between life and death for
vulnerable populations, Wehner said.<br>
<br>
"It's the extreme weather that impacts human health; this week
could be 2 degrees Celsius hotter than last week, and that
doesn't matter," he said. "Now, imagine the hottest day that
you can remember and instead of 42 degrees C (107.6 degrees F) it's
now 45 degrees C (113 degrees F). That's going to have a dangerous
impact on the poor, the old and the very young, who are typically the
ones dying in heat waves."<br>
<br>
By 2075, the situation is likely to become much more dire if
greenhouse gas emissions-produced largely by the burning of fossil
fuels-are not reduced. The percent of land areas subject to 20-year
events that are at least 5 degrees C hotter swells from 10 to 54
percent.<br>
<br>
However, if emissions are aggressively cut, the severity of these
20-year events could be significantly reduced over the majority of the
world's land areas, though portions of the Earth would still face
dangerous heat extremes. For example, in 2075, almost a
quarter-instead of more than a half-of land areas could experience
20-year heat waves that are at least 5 degrees C hotter than today's.
"But even with such dramatic reductions in carbon dioxide
emissions, future heat waves will be far more dangerous than they are
now," Wehner said.</font></div>
<div><font face="Lucida Grande"><br>
The researchers also looked at single-day extreme heat events, as well
as single-day and three-day blocks when the overnight low temperature
remained exceptionally warm. Past research has shown that human health
is especially endangered when temperatures do not cool off
significantly at night. All of these events had similar increases in
frequency and intensity.<br>
<br>
<b>A TOOL FOR COST-BENEFIT ANALYSIS</b><br>
The fact that extreme heat events are expected to increase in the
future as the climate changes-and the fact that emission reductions
could ameliorate that increase-is not a surprise, Tebaldi said. But
this study is important because it puts hard numbers to the
problem.<br>
<br>
"There is a cost attached to reducing emissions," Tebaldi
said. "Decision makers are interested in being able to quantify
the expected benefits of reductions so they can do a cost-benefit
analysis."<br>
Tebaldi and Wehner's paper is part of a larger project based at NCAR
called the Benefits of Reduced Anthropogenic Climate Change, or BRACE.
For the project, researchers from across NCAR and partner
organizations are working to quantify how emission reductions may
affect health, agriculture, hurricanes, sea level rise, and
drought.<br>
<br>
<b>About the article</b><br>
<b>Title:</b> Benefits of mitigation for future heat extremes under
RCP4.5 compared to RCP8.5<br>
<b>Authors:</b> Claudia Tebaldi and Michael F. Wehner<br>
<b>Publication:</b> Climatic Change<br>
<br>
<b>Writer:</b><br>
Laura Snider, Senior Science Writer and Public Information Officer<br>
<br>
<br>
<b>*Media & nonprofit use of images: </b>Except where
otherwise indicated, media and nonprofit use permitted with credit as
indicated above and compliance with UCAR's terms of use. Find
more images in the NCAR|UCAR Multimedia & Image
Gallery.</font></div>
<div><font face="Lucida Grande"><br></font></div>
<div><font face="Lucida Grande">The University Corporation for
Atmospheric Research manages the National Center for Atmospheric
Research under sponsorship by the National Science Foundation. Any
opinions, findings and conclusions, or recommendations expressed in
this publication are those of the author(s) and do not necessarily
reflect the views of the National Science Foundation.</font></div>
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color="#000000"
>=============================================================<br>
" Š organisms have a physiological response to temperature,
and these responses have important consequences Š. biological rates
and times (e.g. metabolic rate, growth, reproduction, mortality and
activity) vary with temperature.<br>
<br>
Anthony I. Dell, Samraat Pawar and Van M. Savage. Temperature
dependence of trophic interactions are driven by asymmetry of species
responses and foraging strategy.<i> Journal of Animal Ecology</i>
2013<x-tab> </x-tab><br>
===========================================================</font></div
>
<div><font face="Verdana" size="-1" color="#000000">"All
organisms live within a limited range of body temperatures, due to
optimized structural and kinetic coordination of molecular, cellular,
and systemic processes. Functional constraints result at temperature
extremes. Increasing complexity causes narrower thermal windows for
whole-organism functions than for cells and molecules, and for animals
and plants than for unicellular organisms (8). Direct effects of
climatic warming can be understood through fatal decrements in an
organism's performance in growth, reproduction, foraging, immune
competence, behaviors and competitiveness. Performance in animals is
supported by aerobic scope, the increase in oxygen consumption rate
from resting to maximal (9). Performance falls below its optimum
during cooling and warming. At both upper and lower pejus
temperatures, performance decrements result as the limiting capacity
for oxygen supply causes hypoxemia (4, 8) (see the figure, left).
Beyond low and high critical temperatures, only a passive, anaerobic
existence is possible."<br>
<br>
Hans O. Pörtner and Anthony P. Farrell. Physiology and Climate
Change.<i> SCIENCE</i> 31 OCTOBER 2008<x-tab> </x-tab>VOL 322<br>
===============================================================<br>
"Between 1C and 2C increases in global mean temperatures most
species, ecosystems and landscapes will be impacted and adaptive
capacity will become limited. With the already ongoing high rate of
climate change, the decline in biodiversity will therefore accelerate
and simultaneously many ecosystem services will become less
abundant."</font></div>
<div><font face="Verdana" size="-1" color="#000000"><br>
Rik Leemans and Bas Eickhout. Another reason for concern: regional and
global impacts on ecosystems for different levels of climate
change.<i> Global Environmental Change</i> 14 (2004)
219-228</font></div>
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