Climate change and the ArcticDaniel J. Jacob, Harvard University

Where is the Arctic sea ice today?

http://nsidc.org/arcticseaicenews/

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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!