NASA scientists described a recent “global warming
hiatus” that shows Earth’s surface temperatures warming at a slower rate than
previous decades – but it is still warming.
Norman Loeb delivered a lecture entitled, “The
Recent Pause in Global Warming: A Temporary Blip or Something More Permanent?”
at the NASA Langley Research Center auditorium on Tuesday. The talk addressed
challenges to scientists and increased skepticism among climate change
skeptics due to the recent “hiatus” of global warming.
The federal space agency climate scientist explored
research into a slow-down in surface warming over the last 15 years referred to
as the “Global Warming Hiatus.” In recent years, the global mean surface
temperature on Earth has increased at a rate that is about one-third of that
from the past 60 years.
The global warming hiatus occurred despite
record-breaking temperatures in the 2000s, retreating Arctic sea ice, rising
sea levels and a record high global concentration of carbon dioxide in the
atmosphere, according to a statement released by NASA.
“Opinions vary about the hiatus, as some view it as
evidence that man-made global warming is a myth,” NASA said in a press release.
“Others explain that it is simply due to climate variability that is
temporarily masking a longer-term temperature trend.”
“The question is what’s driving it?” said Loeb,
according to the Virginian-Pilot.
But his answer reflected the complexity of climate science and did not rule out
either scenario based upon the last 15 years of the “global warming hiatus.”
Loeb said that changes in solar radiation, water
vapor and aerosol particles in the air have likely played a role, but a major
factor may be an El Nino-like pattern of climate variability that has
historically coincided with a slowing in global warming. Loeb noted that a rise
in global temperatures slowed in the 1940s as the Pacific Decadal Oscillation
climate pattern was active – a pattern that similarly lasted 20-30 years.
“For average climate records, 30 years is like one
data point,” said Loeb, reiterating that while the Earth is warming more
slowly, it is still warming. “It’s really forcing us to look at our models and
observations and ask questions.”
In the global warming slowdown of the past 15 years,
Loeb points out that the temperature is rising at nearly one-third the rate as
before. The average temperature in the U.S. has risen about 1.5 degrees since
the beginning of the 1900s.
Loeb holds a doctorate in in atmospheric sciences
from McGill University in Montreal, Canada, and is an atmospheric scientist in
the Science Directorate at NASA Langley. Loeb is also the principal
investigator of a satellite project called Clouds and the Earth’s Radiant Energy
System (CERES).
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