Climate change and the Arctic Daniel J. Jacob, Harvard University.
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Transcript of Climate change and the Arctic Daniel J. Jacob, Harvard University.
Climate change and the ArcticDaniel J. Jacob, Harvard University
Where is the Arctic sea ice today?
http://nsidc.org/arcticseaicenews/
Youare here
The Gulf Stream keeps our sector of the Arctic warm
Seasonal variation in Arctic sea ice (2014)
Marchmaximum
Septemberminimum
1970s data shown as hatched
Murmansk
http://nsidc.org/arcticseaicenews/
Boston Globe, July 12, 2015
Barrow, Alaska
EQUILIBRIUM CLIMATE OF THE EARTH:BALANCE BETWEEN SOLAR AND TERRESTRIAL RADIATION
SOLARRADIATION
(visible)
30% reflected by clouds, ice… TERRESTRIALRADIATION(infrared)
WARMING OF EARTH’S SURFACE BY GREENHOUSE GASES
SOLARRADIATION
(visible)
TERRESTRIALRADIATION(infrared)
Greenhouse gases inatmosphere absorbinfrared radiation, re-emitIt both upward and downward
30% reflected by clouds, ice…
Water and CO2 are the two most important greenhouse gases
Greenhouselayer
CO2 is increasing because of combustion of fossil fuels
Surface observations since 1958 Mauna Loa, Hawaii South Pole
IPCC [2007, 2014]
Ice core records for past 1,000 years
9.5 billion tons of carbonper year (2011)
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 anomalyrelative to 1951-1980 mean;Snowmageddon in Boston
GISTEMP [2015]
Cause: meandering of the jet stream,resulting in an “Arctic vortex”
The Arctic is warming faster than anywhere else on Earth
Shrinking extent of Arctic sea ice, 1979-present
Annual surface temperature trend, 1901-present
IPCC [2014]
summer data
Melting land ice and sea level rise
thermalexpansion
glaciers
Greenland
Antarctica
land storage
IPCC [2014]
Sea level has risen 7 inches since 1900
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
extremelyaggressiveintervention
today
What does this mean for future climate change?
business-as-usualscenario: 8oF warmingby 2100
extremely aggressiveIntervention: climatestabilization by 2040
IPCC [2014]
Projections of future sea-level rise
IPCC [2014]
Limiting future rise to 1 foot will requireextremely aggressive intervention
No ice anywhwere on Earth- crocodiles on Greenland- pine forest in Antarctica- sea level 100 m higher than today
Eocene (55-36 million years ago): last time CO2 was above 500 ppm
Could abrupt climate change take us back to Eocene conditions?
Equilibrium climates of the Earth
ENERGY
TEMPERATURE
Stable climate 1Stable climate 2
Stable climate 3
Perturbationvariabilitéinterannuelle
negative feedback
positivefeedback
abrupt climate change
Temperature and CO2 in ice corestell the story of abrupt climate change
glacial glacial glacial glacial
What can we do?Reduce consumption of fossil fuels: essential strategy for long term
Present-day per capita emission of CO2
US: 5 tons per capita per year (200 lbs per week)
Aggressively reduce consumption of fossil fuels: energy conservation, renewable sources
What can we do?Climate engineering – reflecting solar radiation to space, sequestering carbon… … but
we need to worry about unintended consequences!
