1. Climate change and the Arctic Daniel J. Jacob, Harvard University

2. Where is the Arctic sea ice today? http://nsidc.org/arcticseaicenews/ You are here

3. The Gulf Stream keeps our sector of the Arctic warm

4. Seasonal variation in Arctic sea ice (2014) March maximum September minimum 1970s data shown as hatched Murmansk http://nsidc.org/arcticseaicenews/

5. Boston Globe, July 12, 2015 Barrow, Alaska

6. EQUILIBRIUM CLIMATE OF THE EARTH: BALANCE BETWEEN SOLAR AND TERRESTRIAL RADIATION SOLAR RADIATION (visible) 30% reflected by clouds, ice… TERRESTRIAL RADIATION (infrared)

7. WARMING OF EARTH’S SURFACE BY GREENHOUSE GASES SOLAR RADIATION (visible) TERRESTRIAL RADIATION (infrared) Greenhouse gases in atmosphere absorb infrared radiation, re-emit It both upward and downward 30% reflected by clouds, ice… Water and CO 2 are the two most important greenhouse gases Greenhouse layer

8. CO 2 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 carbon per year (2011)

9. Global surface temperature trend over last 1,000 years IPCC [2007], GISTEMP [2015]

10. 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 GISTEMP [2015] Cause: meandering of the jet stream, resulting in an “Arctic vortex”

11. 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

12. Melting land ice and sea level rise thermal expansion glaciers Greenland Antarctica land storage IPCC [2014] Sea level has risen 7 inches since 1900

13. 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

14. Development of the Harvard Allston campus: consideration of sea-level rise out to 2200

15. Future projections of CO 2 emissions IPCC Representative Concentration Pathways (RCP) CO 2 concentration Emission business as usual extremely aggressive intervention today

16. What does this mean for future climate change? business-as-usual scenario: 8 o F warming by 2100 extremely aggressive Intervention: climate stabilization by 2040 IPCC [2014]

17. Projections of future sea-level rise IPCC [2014] Limiting future rise to 1 foot will require extremely aggressive intervention

18. 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 CO 2 was above 500 ppm Could abrupt climate change take us back to Eocene conditions?

19. Equilibrium climates of the Earth ENERGY TEMPERATURE Stable climate 1 Stable climate 2 Stable climate 3 Perturbation variabilité interannuelle negative feedback positive feedback abrupt climate change

20. Temperature and CO 2 in ice cores tell the story of abrupt climate change glacial

21. What can we do? Reduce consumption of fossil fuels: essential strategy for long term Present-day per capita emission of CO 2 US: 5 tons per capita per year (200 lbs per week) Aggressively reduce consumption of fossil fuels: energy conservation, renewable sources

22. What can we do? Climate engineering – reflecting solar radiation to space, sequestering carbon… … but we need to worry about unintended consequences!