2017-07-15 11:02:24 UTC
etc -- from climatic averages are doubling within 20-30 years at
Today's Extreme Heat May Become Norm Within a Decade
July 14th, 2017
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When 2015 blew the record for hottest year out of the water, it made
headlines around the world. But a heat record that was so remarkable
only 2 years ago will be just another year by 2040 at the latest,
and possibly as early as 2020, regardless of whether the greenhouse
gas emissions warming the planet are curtailed.
That is the conclusion of a new study that uses climate models to
project when today's climate extremes will become commonplace - or the
"new normal" as they are often called in both media reports and
Weather stations in the US that are having a warmer than normal,
colder than normal and record hot year.
Just how soon that record heat will become the norm surprised even its
researchers, but the information could be useful to officials around
the world trying to plan for the changes global warming will bring to
their cities and countries. It will help show when notable heat waves,
downpours, or other extremes may become run-of-the-mill, and would
allow planners to develop the infrastructure and policies to withstand
"At the moment, it doesn't seem like such a big deal when we have
record-hot summers or years," study leader Sophie Lewis, a climate
researcher at Australian National University, said in an email. "But
this study really shows the nasty side of our current records becoming
more frequent in the near future."
While the phrase new normal has been used in different ways, it was
rarely explicitly defined, so Lewis and her colleagues wanted to come
up with a definition that could be used on all kinds of climate extremes.
The team used the climate models developed for the most recent report
of the Intergovtal Panel on Climate Change to see when a global
temperature like that of 2015, or higher, becomes normal. When such
temperatures happened at least half the time in a 20-year period, they
defined that normal as having been reached in the first year of the period.
(The average global temperature of 2015 was 0.23°F (0.13°C) warmer
than the previous warmest year, 2014, according NASA. It was the
second largest year-over-year jump. 2015 was subsequently beaten as
the hottest year by 2016.)
The researchers found that the global climate firmly met that
threshold by 2040, regardless of whether greenhouse gas emissions
continued on their current path or were significantly curtailed. On
average, the new normal emerged between 2020 and 2030 - much earlier
than any of the scientists expected.
"I was shocked when I made the first calculations for this study, and
went back and checked everything twice and then 3 times," Lewis
said. "When I first shared a full draft with my co-authors, I remember
getting an edit back that included a swear word in the comments about
Deke Arndt, a National Oceanic and Atmospheric Administration climate
scientist who wasn't involved in the study, said this kind of
disappearance of extremes into the bounds of normal was already
happening. He cited the then-record high temperature of 1998, "which
was astonishing at the time," but has since been "fading into the
pack" of annual temperatures. (It now sits in eighth place, according
to NOAA, and is the only year in the top 10 warmest not from the 21st
"We are moving into new neighborhoods in many of our climate
variables. This paper is perhaps a way to help quantify some
discussions around that topic," Arndt said.
"I think it's useful that they're defining [the new normal]," Noah
Diffenbaugh, a Stanford climate scientist who has done similar work,
The work, published in the June issue of the Bulletin of the American
Meteorological Society, takes the opposite tack of the field of
climate science known as attribution, which uses observations and
climate models to conduct climatological autopsies of events.
Attribution is useful in gleaning the effect that global warming is
already having on today's extreme weather, but it doesn't say anything
about when those extremes stop being extremes and start becoming the
"It is useful for preparing for the risks of climate change to know
that the 2013 record-hot Australia summer was 5 times more likely
because of climate change, but it is more useful to know that within
just a few decades this extreme could be mild," Lewis said.
Lewis and her co-authors also looked at record annual temperatures at
spots across the land surface, "because these are a little more
relevant for actual impacts on ecosystems, health, infrastructure than
global average temperatures," Lewis said.
In that case, the particular emissions scenarios did make a
difference, because different parts of the world are warming at
different rates and have different patterns of natural variability,
which can make the signal of warming more difficult to pick
out. Today's record heat became the new normal earlier and for a
larger portion of the globe with higher greenhouse gas emissions than
for lower ones. Those differences show that if emissions are
significantly reduced, such records can be prevented from becoming the
norm in some areas.
The method can be further drilled down to study specific extreme
events, like heat waves, droughts or floods, which Lewis said the team
is hoping to do.
Arndt said this is where such a method would have the most
usefulness. "Where I think this approach may have real utility is to
help people process and understand things at the local level," he
said. "Global temperature is an important climate marker, but it's not
the design metric for your town's wastewater treatment or storm sewers."
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Andy Skuce @andyskuce 14 Jul 2017 18:17Z
Just 6% chance of a record for 2017; 64% chance of second place; 30% chance
climatehawk1 @climatehawk1 14 Jul 2017 18:18Z
#Climate fact: The international panel on climate (IPCC) is cautious, not
alarmist, w/ its predictions. http://crwd.fr/2tmHPXW
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