NATS 101 Lecture 25 Climate Change (cont’d)

1. NATS 101 Lecture 25Climate Change (cont’d)

2. The Natural Greenhouse Effect: clear sky CH4 N20 6% O3 8% Water Vapor 60% Carbon Dioxide 26% Clouds also have a greenhouse effect Kiehl and Trenberth 1997

3. CO2 makes the biggest contribution to the climate forcing

4. Global Warming Potential (GWP) Different gases has different warming potentials which are defined relative to the warming effect of CO2 GasGWP Carbon dioxide (CO2) 1 Methane (CH4) 21 Nitrous oxide (N2O) 310 Hydrofluorocarbons 560-12,100 Perfluorocarbons 6,000-9,200 Sulfur hexafluoride 23,900 Ahrens, Fig 2.10

5. ChangingCO2 concentrations • CO2 concentrations have varied naturally by ~30-50% over the past few hundred thousand years (ice ages) • Fossil fuel burning since the industrial revolution has created a recent sharp increase in CO2 concentrations • CO2 concentrations are now higher than at any time in past few hundred thousand years • And concentrations are increasing faster with time Last 4 Ice Age cycles: 400,000 years Man made You are here See http://epa.gov/climatechange/science/recentac.html

6. CO2 Temp.

7. IncreasingCO2 concentrations • How high will they go? How warm will it get??? • If CO2 concentrations stay within factor of 2 of pre-industrial, then warming of 3+1oC is expected • If concentrations go still higher => larger uncertainty because the climate is moving into unprecedented territory See http://epa.gov/climatechange/science/futureac.html You are going to be somewhere in here Last 4 Ice Age cycles: 400,000 years Man made You are here Ice age CO2 range

8. Predictions of increased CO2 & Temperature Emissions High Medium Low Constant 2000 CO2 Multi-model global averages of surface warming (relative to 1980-99) for the scenarios A2, A1B and B1, as continuations of the 20th century simulations. Shading is plus/minus one standard deviation range of individual model annual averages. Trenberth/IPCC

9. Missing Carbon Sink • CO2 is accumulating in the atmosphere more slowly than expected (believe it or not) • Based on our understanding of CO2 emissions and ocean and atmosphere uptake, there is a missing sink/uptake of about 25% Woods Hole web page NASA OCO mission

10. Ocean Carbon Uptake

11. Ocean Uptake of CO2 SciAm article

12. The Oceans & Global Change • Much of this material is courtesy of • Julia Cole, here in Geosciences at UA and • Kevin Trenberth at the National Center for Atmospheric Research [NCAR]

14. Ocean Transport of Heat

15. 3D “Conveyor Belt” Concept

16. Potential Changes Related to the Ocean

17. Change in Thermohaline Circulation

18. Change in Ocean Chemistry

19. Ocean Acidification (SciAm article) • Currently ~1/3 of CO2 released by burning fossil fuels ends up in the ocean. • Absorbed CO2 forms carbonic acid in seawater, lowering the slightly alkaline pH level, changing the balance of carbonate & bicarbonate ions. • Shift toward acidity & ensuing changes in ocean chemistry, make it more difficult for creatures to build hard parts out of calcium carbonate. • Decline in pH thus threatens a variety of organisms, including corals, which provide one of the richest habitats on earth. • Within a century, Southern Ocean surface will be corrosive to shells of tiny snails key in the marine food chain within this highly productive zone.

20. Sea level is rising: from ocean expansion and melting glaciers • Since 1993 • Global sea level • has risen 43 mm • (1.7 inches) • 60% from • expansion as ocean temperatures rise, • 40% from melting glaciers from Steve Nerem via Trenberth

21. Observed Ocean Warming • Most oceans are warming • Figures from Hansen et al 2006

22. Evidence for reality of climate change Glaciers melting Muir Glacier, Alaska 1909 Toboggan Glacier Alaska 2000 1900 2003 Alpine glacier, Austria

23. Research indicates that less than8°F of Arctic warmingcaused Greenland to lose enough water toraise sea level by up to 12 feet during the Last Interglacial Period Today 125,000 years ago Image from Bette Otto-Bliesner, National Center for Atmospheric Research

24. BUT, sea level rise during the Last Interglacial Period appears to have been more… it was likely up to21 feet. A reduced Greenland Ice Sheet could only have contributed up to12 feet… Where did the rest of the water come from?

25. Today Most likely Antarctica… East Antarctic Ice Sheet West Antarctic Ice Sheet http://svs.gsfc.nasa.gov

26. 125,000 years ago - the West Antarctic Ice Sheet may have been gone East Antarctic Ice Sheet Late Quaternary diatoms and anomalously high 10Be found in sediments under the ice sheet

27. 1 meter 2 meters www.gfdl.noaa.gov 4 meters 8 meters

28. Surface melt on Greenland Increasing melt zones. Melt descending into a moulin: a vertical shaft carrying water to the base of the ice sheet. NSIDC (above) Braithwaite: Univ. Manchester

29. Greenland ice mass budget A great deal of effort is going into estimating how the Greenland ice sheet is changing Researchers Mass ChangeMethodTime Span (GT/year) Krabill et al. 2000 -47Aircraft Surveys1994-1999 Velicogna et al. 2006 -200 to -260GRACE2002-2006 Luthcke et al. 2007* -145 to -175GRACE2003-2006 Zwally et al. 2007* -80 to -100ICESat2003-2005 GRACE is a gravity recovery mission ICESat is a lidar topographymission NASA website on Greenland ice sheet 100 GT/yr ~ 0.3 mm/yr sea level rise

30. Snow cover and Arctic sea ice are decreasing Arctic sea ice area decreased by 2.7% per decade (Summer: -7.4%/decade) 2007: 22% (106 km2) lower than 2005 Spring snow cover shows 5% stepwise drop during 1980s Trenberth/IPCC

31. Arctic sea ice disappears in summer by 2050 Already 2007 lowest on record by 22% Abrupt Transitions in Summer Sea Ice • Gradual forcing results in abrupt Sept ice decrease • Extent decreases from 80 to 20% coverage in 10 years. • Relevant factors: • Ice thinning • Arctic heat transport • Albedo feedback 2007 x Trenberth from Holland et al., GRL, 2006

32. Land surface temperatures are rising faster than SSTs SST Land Annual anomalies of global average SST and land surface air temperature Land increased 0.4oC vs ocean suggesting 3% decrease in RH over land Trenberth/IPCC

33. Controlling Heat Human body: sweats Homes: Evaporative coolers (swamp coolers) Planet Earth: Evaporation (if moisture available) e.g., When sun comes out after showers, the first thing that happens is that the puddles dry up: before temperature increases. Trenberth

34. Water vapor increase at higher temperatures Water holding capacity of atmosphere increases about 7% per oC (4% per F) increase in temperature. Observations show that water vapor in LOWER troposphere is indeed increasing. Surface temperature increase: 0.6C since 1970 over global OCEANS and 4% more water vapor. Total water vapor Since late 1970’s, ocean surface has been warming at ~0.14C/decade => ~1% WV increase/decade. Observed WV trend since 1988 is ~1.2% per decade From Trenberth/IPCC

35. Increases Decreases Land precipitation is changing significantly over broad areas Smoothed annual anomalies for precipitation (%) over land from 1900 to 2005; other regions are dominated by variability. Trenberth/IPCC

36. Proportion of heavy rainfalls: increasing in most land areas Regions of disproportionate changes in heavy (95th) and very heavy (99th) precipitation Trenberth/IPCC

37. Declining Snow Pack in many mountain and continental areas contributes to drought • moreprecipitationfalls as rain rather than snow, especially in the fall and spring. • snow meltoccurs faster and sooner in the spring • snow packis therefore less • soil moistureis less as summer arrives • the risk of droughtincreases substantially in summer • Along with wild fire Trenberth

38. Drought is increasing most places Mainly decrease in rain over land in tropics and subtropics, but enhanced by increased atmospheric demand with warming The most important spatial pattern (top) of the monthly Palmer Drought Severity Index (PDSI) for 1900 to 2002. The time series (below) accounts for most of the trend in PDSI. Trenberth/IPCC

39. Rising greenhouse gases are causing climate change, and arid areas are becoming drier while wet areas are becoming wetter. Water management:- dealing with how to save in times of excess for times of drought – will be a major challenge in the future. Trenberth Lake Powell

40. Heat waves and wild fires Impacts on human health and mortality, economic impacts, ecosystem and wildlife impacts Trenberth

41. Extremes of temperature are changing! Observed trends (days) per decade for 1951 to 2003: 5th or 95th percentiles From Alexander et al. (2006) Trenberth/IPCC

42. Global Atmo Energy Imbalance Increasing GHG concentrations decrease Energy out So Energy IN > Energy OUT and the Earth warms IR Out is reduced Ahrens, Fig. 2.14 Solar in Atmosphere

43. Trend plus variability? Heat waves are increasing: an example Extreme Heat Wave Summer 2003 Europe 30,000 deaths Trenberth/IPCC

44. Trenberth

45. CO2 emissions in different regions in 2000 in terms of emissions per capita (height of each block); population (width of each block); and total emissions (product of population and emissions per capita = area of block). Source: M. Grubb, http://www.eia.doe.gov/iea/ Trenberth

46. Trenberth