1. NATS 101 Lecture 33 Climate Change (cont’d)

2. Absorption 20% of incident Visible (0.4-0.7  m) is absorbed O 2 an O 3 absorb UV (shorter than 0.3  m) Infrared (5-20  m) is selectively absorbed H 2 O & CO 2 are strong absorbers and emitters of IR Little absorption of IR around 10  m – atmospheric window Visible IR Ahrens, Fig. 2.9

3. WaterVapor60% CarbonDioxide26% O 3 8% CH 4 N 2 0 6% 6% Clouds also have a greenhouse effect Kiehl and Trenberth 1997 The Natural Greenhouse Effect: clear sky

4. CO 2 makes the biggest contribution to the climate forcing

5. Global Warming Potential (GWP) Different gases has different warming potentials which are defined relative to the warming effect of CO 2 Ahrens, Fig 2.10 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

6. Changing CO 2 concentrations CO 2 concentrations measured very precisely since 1958 Over past 45 years they’ve increased by ~21% Present 0.6%/yr increase See http://www.cmdl.noaa.gov/ccgg/trends/co2_data_mlo.php http://www.cmdl.noaa.gov/ccgg/trends/co2_data_mlo.php You are here

7. Data from Climate Monitoring and Diagnostics Lab., NOAA. Data prior to 1974 from C. Keeling, Scripps Inst. Oceanogr. Changing atmospheric composition: CO 2 Mauna Loa, Hawaii Changing atmospheric composition: CO 2 Mauna Loa, Hawaii Over past 45 years they’ve increased by ~21% Present 0.6%/yr increase

8. Source: Hansen, Climatic Change 2005, based on Petit, Nature 1999 Context: 400,000 years of Antarctic ice core records of Temperatures, Carbon dioxide and Methane. Last ice age glacial: 20,000 years ago

9. Changing CO 2 concentrations CO 2 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 CO 2 concentrations CO 2 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 See http://epa.gov/climatechange/science/recentac.html Man made You are here

10. CO 2 Temp.

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

12. 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 Constant 2000 CO 2 Emissions High Medium Low Predictions of increased CO 2 & Temperature

13. Missing Carbon Sink CO 2 is accumulating in the atmosphere more slowly than expected (believe it or not) Based on our understanding of CO 2 emissions and ocean and atmosphere uptake, there is a missing sink/uptake of about 25% NASA OCO mission Woods Hole web page

14. Ocean Carbon Uptake

15. Ocean Uptake of CO 2 SciAm article

16. 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]

18. Ocean Transport of Heat

19. 3D “Conveyor Belt” Concept

20. Potential Changes Related to the Ocean

21. Change in Thermohaline Circulation

22. Change in Ocean Chemistry

23. Ocean Acidification (SciAm article)SciAm article Currently ~1/3 of CO 2 released by burning fossil fuels ends up in the ocean. Absorbed CO 2 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.

24. 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 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 Sea level is rising:

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

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

27. Today 125,000 years ago Research indicates that less than 8°F of Arctic warming caused Greenland to lose enough water to raise sea level by up to 12 feet during the Last Interglacial Period Image from Bette Otto-Bliesner, National Center for Atmospheric Research

28. BUT, sea level rise during the Last Interglacial Period appears to have been more… it was likely up to 21 feet. A reduced Greenland Ice Sheet could only have contributed up to 12 feet … Where did the rest of the water come from?

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

30. 125,000 years ago - the West Antarctic Ice Sheet may have been gone East Antarctic Ice Sheet Late Quaternary diatoms and anomalously high 10 Be found in sediments under the ice sheet

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

32. 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 Surface melt on Greenland

33. Greenland ice mass budget Researchers Mass Change Method Time Span (GT/year) Krabill et al. 2000 -47 Aircraft Surveys 1994-1999 Velicogna et al. 2006 -200 to -260 GRACE 2002-2006 Luthcke et al. 2007* -145 to -175 GRACE 2003-2006 Zwally et al. 2007* -80 to -100 ICESat 2003-2005 GRACE is a gravity recovery mission ICESat is a lidar topographymission NASA website on Greenland ice sheet A great deal of effort is going into estimating how the Greenland ice sheet is changing 100 GT/yr ~ 0.3 mm/yr sea level rise

34. Snow cover and Arctic sea ice are decreasing Spring snow cover shows 5% stepwise drop during 1980s Arctic sea ice area decreased by 2.7% per decade (Summer: -7.4%/decade) 2007: 22% (10 6 km 2 ) lower than 2005 Trenberth/IPCC

35. 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 Trenberth from Holland et al., GRL, 2006 2007 x

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

37. Human body: sweats Homes: Evaporative coolers (swamp coolers) Planet Earth: Evaporation (if moisture available) 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

38. Total water vapor 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. Water holding capacity of atmosphere increases about 7% per o C (4% per  F) increase in temperature. From Trenberth/IPCC 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 Water vapor increase at higher temperatures

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

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

41. more precipitation falls as rain rather than snow, especially in the fall and spring. snow melt occurs faster and sooner in the spring snow pack is therefore less soil moisture is less as summer arrives more precipitation falls as rain rather than snow, especially in the fall and spring. snow melt occurs faster and sooner in the spring snow pack is therefore less soil moisture is less as summer arrives the risk of drought increases substantially in summer Along with wild fire the risk of drought increases substantially in summer Along with wild fire Declining Snow Pack in many mountain and continental areas contributes to drought Trenberth

42. 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. Drought is increasing most places Mainly decrease in rain over land in tropics and subtropics, but enhanced by increased atmospheric demand with warming Trenberth/IPCC

43. 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. 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. Lake Powell Trenberth

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

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

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

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

48. Trenberth

49. 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