Scientists are 95% certain that human activity has caused at least half
of climate change in the last 50 years, a U.N. report concludes.
FULL STORY
September 27, 2013 -- Updated 1256 GMT (2056 HKT)
Understanding the climate change report
STORY HIGHLIGHTS
- NEW: Climate change deniers beware, says Secretary of State John Kerry
- There is even more certainty that humans are playing a role
- The report lays out projections for climate change through the end of the century
- The first section of the report is aimed at assisting policymakers
That activity? Driving
cars, running power plants on coal and oil, torching swathes of
forestland and debris; anything involving burning carbon-based fuels and
emitting greenhouse gases.
We are seeing the
consequences already in extreme weather patterns, particularly drought
and flood, and they will probably get worse this century, the report
said.
"It should serve as yet
another wake-up call our activities today have a profound impact on
society, not only for us, but for many generations to come," Michel
Jarraud, head of the World Meteorological Organization, said at a news
conference in Stockholm, Sweden.
Saving the coral reefs
Scottish salmon fisheries imperiled
U.S. Secretary of State John Kerry echoed his words in an official statement.
"Those who deny the
science or choose excuses over action are playing with fire," he said.
"Once again, the science grows clearer, the case grows more compelling,
and the costs of inaction grow beyond anything that anyone with
conscience or common sense should be willing to even contemplate."
The assessment report
from the Intergovernmental Panel on Climate Change is the benchmark
study on global warming published every few years. Nearly 1,000
researchers from around the world work on the document, which then
undergoes review by about as many scientists.
The panel released a summary report Friday and plans to post the full version, roughly 2,500 pages, online on Monday.
This year's report further strengthens the suspicions that scientists already have.
In 2007, climate
researchers were already 90% sure that people were behind a seemingly
small rise in global average temperature of about half a degree Celsius
(1 degree Fahrenheit) that has already notched up extreme weather events
such as heat waves, droughts and flooding.
The effects they are
already causing are expected to increase for a century or more, the
report reads. Weather catastrophes, previously called storms of the
century, are on their way to striking every 20 years or even more
frequently.
This means,
unfortunately, that we could see more EF5 tornadoes like the one that
ground up Moore, Oklahoma; stronger and more floods like those that
inundated Colorado towns; another Sandy or Katrina or two in our
lifetimes; more crops wiped out by drought; and more forestland consumed
by roaring wildfires.
The Arctic ice cap could
melt nearly completely in summer, and sea levels could continue to
rise. In the Antarctic, the ice cap could continue to increase slightly.
And if greenhouse gas
emissions continue to climb as they have, the resulting temperature rise
and its deadly effects would get even worse, the report says.
Hundreds of experts weigh in
The 2013 assessment
report from the Intergovernmental Panel on Climate Change brings
together the latest research from top scientists in the field. It
contains a "summary for policymakers" aimed at guiding politicians and
lawmakers worldwide on decisions regarding the environment over the next
several years.
The document released Friday explains the physical science behind climate change.
The U.N. panel releases a
report every five or six years. Friday's report is the culmination of
work by more than 250 authors from 39 countries and was subject to an
extensive review process involving more than 1,000 experts.
More than 850 expert
authors from 85 countries contributed research for the full report,
which will be released in three stages through April. The first, on the
physical science behind climate change, accompanies the summary for
policymakers. The second, expected in March, will cover "impacts and
vulnerabilities" of climate change; the third, on mitigation efforts, is
set to go out in April.
Critics of the report
Despite the breadth of
the scientific expertise involved and the extensive review and approval
process, the assessment reports spark quite a few criticisms, from both
climate change believers and skeptics.
Skeptics say the panel
exists only to produce further evidence supporting the idea of man-made
climate change while ignoring opposing research. But climate change
activists, and many climate scientists, say the panel's
consensus-seeking policy produces conclusions and estimates that are too
conservative.
Another often-cited
critique of the report is that, due to its size and lengthy approval
process, it is already outdated by the time it is released. Several
important studies already have been published in the past year in the
constantly evolving science of climate change that will not be included
in this assessment.
Despite the critics,
this week's document will serve as a major measuring stick for the
current state of the world's climate and what type of change is in
store.
The summary for policymakers will be available Friday at www.climatechange2013.org.
September 27, 2013 -- Updated 1300 GMT (2100 HKT)
A U.N. climate panel says in its latest report that it is more confident
than ever that humans are responsible for at least half of temperature
increases since the 1950s. FULL STORY
U.N. climate change report points blame at humans
September 27, 2013 -- Updated 0936 GMT (1736 HKT)
U.N. climate report blames humans
STORY HIGHLIGHTS
- Scientists surer than ever humans play major role in climate change, report says
- Global warming already affecting extreme weather, and it could get worse, report says
- U.N.'s IPCC convenes every six years to put together report; it's considered benchmark on topic
- Even if emissions ended today, effects of climate change could linger for centuries
So says a report from the U.N. International Panel on Climate Change,
a document released every six years that is considered the benchmark on
the topic. More than 800 authors and 50 editors from dozens of
countries took part in its creation.
The summary for
policymakers was released early Friday, while the full report, which
bills itself as "a comprehensive assessment of the physical science
basis of climate change," will be distributed Monday. Other reports,
including those dealing with vulnerability and mitigation, will be
released next year.
Here are the highlights from Friday's summary:
Man-made climate change is almost certain
Greenland adapts to climate change
Understanding the climate change report
Scottish salmon fisheries imperiled
Images help scientists track coral reefs
Climate scientists are
95% confident -- that is to say, surer than ever -- that humans are
responsible for at least "half of the observed increase in global
average surface temperatures since the 1950s."
This is the major
headline from the report, as it marks a stark spike in confidence over
the last 12 years, as scientists were 90% confident in 2007 and 66%
confident in 2001 of the same conclusion.
An increase in carbon
dioxide concentrations that is "unprecedented" in the last 20,000 years,
along with increases in other emissions, have driven up average
temperatures by about 0.6 degrees Celsius (1 degree Fahrenheit) since
1950, the report states.
Worst-case predictions
are that by 2100, temperatures could increase by as much as 3.7 degrees
Celsius (6.6 Fahrenheit), the report says.
Climate change is already affecting extreme weather
Since 1950 we've seen a
dramatic increase in extreme weather. This is especially true of record
heat and heavier precipitation events.
While it's difficult to
determine the exact role climate change plays in an individual event,
such as Hurricane Sandy or the EF-5 tornado that struck Moore, Oklahoma,
because there are so many ingredients necessary to brew a single storm,
the links are clearer when you look at overall patterns.
According to a study
released this month in the Bulletin of the American Meteorological
Society, scientists found strong links between global warming and extreme weather around the globe in 2012.
Among the 2012 events
were the July heat wave in the northeastern and north-central United
States, the spring heat wave in the eastern United States, the Great
Plains drought, the winter drought in Spain and Portugal and the heavy
rains and flooding in Europe.
According to a paper in
the journal Nature, this year, weather events that have previously been
classified as "storms of the century" could become the storm of "every
20 years or less."
How cities fight climate change
Scientists 95% sure on climate change
Is climate change causing disasters?
"Climate change will probably increase storm intensity and size simultaneously, resulting in a significant intensification of storm surges," the paper said.
The last 30-year period is "very likely" the warmest in the last 800 years
Scientists are 90% sure
that 1981-2010 was the warmest such span in the last eight centuries,
and there's a 66% chance that it was the warmest 30-year period in the
last 1,400 years.
While the last 15 years
have not warmed as quickly, we've seen steady warming over most of the
globe, and we haven't seen a below-average temperature month since
February 1985.
Scientists are also 99%
certain that we will see more hot days and nights -- and fewer chilly
ones -- as the 21st century progresses.
"Each of the last three
decades has been significantly warmer than all preceding decades since
1850," according to the IPCC report.
To give you an idea of
how the Earth has heated up, the combined land and ocean temperature
increased by about 0.8 degrees Celsius between 1901 and 2010, yet
between 1979 and 2010, the temperature spiked about 0.5 degrees Celsius.
Sea level rise will increase due to warming oceans and loss of ice
Better climate models give scientists more confidence that sea level rise will accelerate in the 21st century.
Scientists are 99% sure
that sea level rise has accelerated over the last 2 centuries at a rate
higher than at any time in the last 2,000 years.
They're also highly
confident that if the global surface temperature increases by more than 2
degrees Celsius over present temperatures we could see "a nearly
ice-free Arctic Ocean in late summer."
The report further notes
that there is increasing evidence that ice sheets are losing mass,
glaciers are shrinking, Arctic sea ice cover is diminishing, snow cover
is decreasing and permafrost is thawing in the Northern Hemisphere.
As for the rise in sea
level, scientists asserted in the IPCC report that tide gauges and
satellite data make it "unequivocal" that the world's mean sea level is
on the upswing.
Even if we end emission tomorrow, climate change could continue for centuries
This may be one of the
more harrowing findings in the report, as it suggests we're too far gone
to effect any meaningful change in our lifetimes.
Even if we end carbon
dioxide emissions today, effects could linger for hundreds, if not
thousands, of years. And certain changes may already be irreversible.
"Many aspects of climate
change will persist for centuries even if concentrations of greenhouse
gases are stabilized. This represents a multicentury commitment created
by human activities today," the report states.
COPY http://edition.cnn.com/
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