Transcript PPT - Harvard University

Climate change and the Arctic
Daniel J. Jacob, Harvard University
Where is the Arctic sea ice today?
You
are
here
http://nsidc.org/arcticseaicenews/
The Gulf Stream keeps our sector of the Arctic warm
Seasonal variation in Arctic sea ice (2014)
1970s data shown as hatched
March
maximum
September
minimum
Murmansk
http://nsidc.org/arcticseaicenews/
Boston Globe, July 12, 2015
Barrow, Alaska
EQUILIBRIUM CLIMATE OF THE EARTH:
BALANCE BETWEEN SOLAR AND TERRESTRIAL RADIATION
SOLAR
RADIATION
(visible)
30% reflected by clouds, ice…
TERRESTRIAL
RADIATION
(infrared)
WARMING OF EARTH’S SURFACE BY GREENHOUSE GASES
SOLAR
RADIATION
(visible)
Greenhouse
layer
30% reflected by
clouds, ice…
Greenhouse gases in
atmosphere absorb
infrared radiation, re-emit
It both upward and downward
TERRESTRIAL
RADIATION
(infrared)
Water and CO2 are the two most important greenhouse gases
CO2 is increasing because of combustion of fossil fuels
Surface observations since 1958
Mauna Loa, Hawaii
South Pole
9.5 billion tons of carbon
per year (2011)
Ice core records for past 1,000 years
IPCC [2007, 2014]
Global surface temperature trend over last 1,000 years
IPCC [2007],
GISTEMP [2015]
There is large year-to-year variation on top of long-term trend
February 2015 temperature anomaly
relative to 1951-1980 mean;
Snowmageddon in Boston
Cause: meandering of the jet stream,
resulting in an “Arctic vortex”
GISTEMP [2015]
The Arctic is warming faster than anywhere else on Earth
Annual surface temperature trend, 1901-present
Shrinking extent of Arctic sea ice, 1979-present
summer data
IPCC [2014]
Melting land ice and sea level rise
Sea level has risen 7 inches
since 1900
land
storage
thermal
expansion
Greenland
glaciers
IPCC [2014]
Very obvious impacts of sea-level rise
Islands, low-lying areas become uninhabitable
4.9 million in US live less than 4ft above sea level
Kiribati
Development of the Harvard Allston campus:
consideration of sea-level rise out to 2200
Future projections of CO2 emissions
IPCC Representative Concentration Pathways (RCP)
CO2 concentration
Emission
business
as usual
today
extremely
aggressive
intervention
What does this mean for future climate change?
business-as-usual
scenario: 8oF warming
by 2100
extremely aggressive
Intervention: climate
stabilization by 2040
IPCC [2014]
Projections of future sea-level rise
Limiting future rise to 1 foot will require
extremely aggressive intervention
IPCC [2014]
Eocene (55-36 million years ago): last time CO2 was above 500 ppm
No ice anywhwere on Earth
- crocodiles on Greenland
- pine forest in Antarctica
- sea level 100 m higher than today
Could abrupt climate change take us back to Eocene conditions?
Equilibrium climates of the Earth
ENERGY
positive
feedback
negative
feedback
abrupt
climate
change
Perturbation
variabilité
interannuelle
Stable climate 2
Stable climate 1
Stable climate 3
TEMPERATURE
Temperature and CO2 in ice cores
tell the story of abrupt climate change
glacial
glacial
glacial
glacial
What can we do?
Reduce consumption of fossil fuels: essential strategy for long term
Aggressively reduce consumption of fossil fuels: energy conservation, renewable sources
Present-day per capita emission of CO2
US: 5 tons per capita per year (200 lbs per week)
What can we do?
Climate engineering – reflecting solar radiation to space, sequestering carbon… …
but we need to worry about unintended consequences!