Geo-engineering of climate

Transcription

1 CREATE Summer School Tim Canty Geo-engineering of climate Today: Climate change Geo-engineering of climate How this may affect the polar regions Will it really work? Lecture C 27 July

2 Is the climate warming? Monthly, global temperature anomaly 2

3 Is the climate warming? Monthly, global temperature anomaly 3

4 Is the climate warming? Monthly, global temperature anomaly 4

5 Is the climate warming? Monthly, land temperature anomaly 5

6 Is the climate warming? Monthly, land temperature anomaly 6

7 Is the climate warming? Monthly, land temperature anomaly 7

8 Is the climate warming? Monthly, land temperature anomaly 8

9 Is the climate warming? Monthly, land temperature anomaly So, the Earth is getting warmer. What s the big deal? 9

10 Consequences of Climate Change as a Function of Future Rise in Globally Averaged T 1 C Increased damage from flooding & storms Coral bleaching 2 C: Severe damage to Arctic, alpine, and coral ecosystems Freshwater resources stressed, leading to widespread crop shortages 3 C: ~30% of global coastal wetlands lost Terrestrial biomass could become net carbon source due to drought, accelerating rise in atmospheric CO 2 4 C: Widespread coral mortality Melting of Ronne and Ross Ice Sheets 5 C: Permanent loss of ice sheets at both poles Loss of ocean clathrates, accelerating rise in atmospheric CH 4 Sources: IPCC 2007 WG2 Figure SPM.2; Six Degrees: Our Future on a Hotter Planet by Mark Lynas; Chris Barnet presentations on Global Warming 10

11 Consequences of Climate Change as a Function of Future Rise in Globally Averaged T 1 C Increased damage from flooding & storms Coral bleaching 2 C: 3 C: Severe damage to Arctic, alpine, and coral ecosystems Freshwater So, resources the Earth stressed, is getting leading warmer. to widespread crop shortages What s the big deal? ~30% of global coastal wetlands lost Terrestrial biomass could become net carbon source due to drought, Hmm OK, what can we do about this? accelerating rise in atmospheric CO 2 4 C: Widespread coral mortality Melting of Ronne and Ross Ice Sheets 5 C: Permanent loss of ice sheets at both poles Loss of ocean clathrates, accelerating rise in atmospheric CH 4 Sources: IPCC 2007 WG2 Figure SPM.2; Six Degrees: Our Future on a Hotter Planet by Mark Lynas; Chris Barnet presentations on Global Warming 11

12 12

13 Atmospheric Radiation Solar irradiance (downwelling) at top of atmosphere occurs at wavelengths between ~200 and 2000 nm (~5750 K black body temperature) Thermal irradiance (upwelling) at top of the atmosphere occurs at wavelengths between ~5 and 50 m (~245 K black body temperature) Panel (a): Curves of black-body energy versus wavelength for 5750 K (Sun s approximate temperature) and for 245 K (Earth s mean temperature). The curves are drawn with equal area since, integrated over the entire Earth at the top of the atmosphere, the solar (downwelling) and terrestrial (upwelling) fluxes must be equal. Panel (b): absorption by atmospheric gases for a clear vertical column of the atmosphere (1.0 represents complete absorption). From Houghton, Physics of Atmospheres,

14 Atmospheric Radiation Solar irradiance (downwelling) at top of atmosphere occurs at wavelengths between ~200 and 2000 nm (~5750 K black body temperature) Thermal irradiance (upwelling) at top of the atmosphere occurs at wavelengths between ~5 and 50 m (~245 K black body temperature) Panel (a): Curves of black-body energy versus wavelength for 5750 K (Sun s approximate temperature) and for 245 K (Earth s mean temperature). The curves are drawn with equal area since, integrated over the entire Earth at the top of the atmosphere, the solar (downwelling) and terrestrial (upwelling) fluxes must be equal. Panel (b): absorption by atmospheric gases for a clear vertical column of the atmosphere (1.0 represents complete absorption). CFC s absorb in the clearest region of the Atmospheric Window From Houghton, Physics of Atmospheres,

15 GWP weighted emissions of CO 2 GWP weighted emissions of CFCs, without early aerosol propellant ban (i.e., no ban on CFCs) GWP weighted emissions of CFCs, without Montreal Protocol ODS Actual Velders et al., PNAS,

16 Geo-engineering of weather & climate has a long history: 1945: John von Neumann and other leading scientists meet at Princeton and agreed that modifying weather deliberately might be possible (motivation was next great war ) 1958: US Congress funded expanded rainmaking research (Irving Langmuir, GE) Cold War: U.S. military agencies devoted significant funds to research on what came to be called "climatological warfare one aim was to make the Arctic Ocean navigable by eliminating the ice pack extensive cloud-seeding conducted over Ho Chi Minh Trail during Vietnam war, to increase rainfall and bog down the North Vietnamese Army's supply line in mud 1975: Mikhail Budyko calculated that if global warming ever became a serious threat, we could counter with just a few airplane flights a day in the stratosphere, burning sulfur to make aerosols that would reflect sunlight away 1977: N.A.S. report looked at a variety of schemes to reduce global warming, should it ever become dangerous, and concluded a turn to renewable energy was a more practical solution than geo-engineering of climate Source: S. Weart, The Discovery of Global Warming, Harvard University Press,

17 Geo-engineering of weather & climate has a long history: Geo-engineering of climate garnered renewed attention with the publication, in August 2006, of an article entitled: Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolved a Policy Dilemma? by Paul J. Crutzen : Climatic Change, 77, ,

18 Geo-engineering of weather & climate has a long history: Geo-engineering of climate garnered renewed attention with the publication, in August 2006, of an article entitled: Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolved a Policy Dilemma? by Paul J. Crutzen : Climatic Change, 77, , 2006 (1995) 18

19 Geo-engineering of weather & climate has a long history: Geo-engineering of climate garnered renewed attention with the publication, in August 2006, of an article entitled: Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolved a Policy Dilemma? by Paul J. Crutzen : Climatic Change, 77, , 2006 (1995) 19

20 Geo-engineering of weather & climate has a long history: Geo-engineering of climate garnered renewed attention with the publication, in August 2006, of an article entitled: Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolved a Policy Dilemma? by Paul J. Crutzen : Climatic Change, 77, , 2006 (1995) major volcanic eruptions can thus cause a drop in global mean surface temperature of about half a degree Celsius that can last for months and even years. IPCC

21 Geo-engineering of climate garnered lots of renewed attention with the publication, in August 2006, of an article entitled: Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolved a Policy Dilemma? by Paul J. Crutzen : Climatic Change, 77, , 2006 According to model calculations complete improvement in air quality could lead to a decadal global average surface air temperature increase by 0.8 K on most continents and 4 K in the Arctic. Further studies indicate that global average climate warming during this century may even surpass the highest values in the projected IPCC global warming range of ºC 21

22 Geo-engineering of climate garnered lots of renewed attention with the publication, in August 2006, of an article entitled: Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolved a Policy Dilemma? by Paul J. Crutzen : Climatic Change, 77, , 2006 According to model calculations complete improvement in air quality could lead to a decadal global average surface air temperature increase by 0.8 K on most continents and 4 K in the Arctic. Further studies indicate that global average climate warming during this century may even surpass the highest values in the projected IPCC global warming range of ºC What aspect of air quality improvement might lead to a large increase in surface air temperature? 22

23 Atmospheric Response to Mt. Pinatubo Mt Pinatubo erupted in June 1991, depositing 6 Tg of sulfur into the stratosphere The Microwave Sounding Unit (MSU) reported global avg d cooling of ~0.5 C Pinatubo Santa María Agung El Chichón Soden et al., Science,

24 Geo-engineering of climate garnered lots of renewed attention with the publication, in August 2006, of an article entitled: Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolved a Policy Dilemma? by Paul J. Crutzen : Climatic Change, 77, , 2006 Requires 5.3 Tg perturbation to stratospheric S to counter requires continuous injection of 2.65 to 5.3 Tg S per year (due to 2 or 1 yr τ STRATOSPHERE ) estimated cost $70 to 140 billion per year ($70 to 140 per capita of affluent world) for comparison: annual military expenditures $1000 billion per year advocates manufacture & surface release of a special gas (insoluble, non-toxic, un-reactive with OH, and zero GWP) that is processed photochemically only in the stratosphere to yield sulfate aerosols (he s an atmospheric chemist!) Ozone depletion Global column O 3 declined by ~2.5% following eruption of Mt. Pinatubo Compensating for CO 2 doubling would lead to less ozone loss than followed Pinatubo Stratospheric chlorine is declining, so enhanced O 3 loss less worrisome in the future 24

25 Geo-engineering of climate garnered lots of renewed attention with the publication, in August 2006, of an article entitled: Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolved a Policy Dilemma? by Paul J. Crutzen : Climatic Change, 77, , 2006 Requires 5.3 Tg perturbation to stratospheric S to counter requires continuous injection of 2.65 to 5.3 Tg S per year (due to 2 or 1 yr τ STRATOSPHERE ) estimated cost $70 to 140 billion per year ($70 to 140 per capita of affluent world) for comparison: annual military expenditures $1000 billion per year advocates manufacture & surface release of a special gas (insoluble, non-toxic, un-reactive with OH, and zero GWP) that is processed photochemically only in the stratosphere to yield sulfate aerosols (he s an atmospheric chemist!) Ozone depletion Global column O 3 declined by ~2.5% following eruption of Mt. Pinatubo Compensating for CO 2 doubling would lead to less ozone loss than followed Pinatubo Stratospheric chlorine is declining, so enhanced O 3 loss less worrisome in the future Will the response of polar ozone to stratospheric sulfur injection be as modest as suggested by the response of global ozone to Mt. Pinatubo aerosol? 25

26 Arctic Ozone Loss vs PSC Exposure update to Rex et al., 2006 PSCs polar stratospheric clouds: provide surfaces for heterogeneous conversion of HCl and ClNO 3 to ClO 26

27 Stratospheric Optical Depth Chlorine activation reactions occur on cold aerosols Chlorine activation depends on T as well as Surface Area Volcanoes provide more reactive surface area than PSCs! Tabazadeh et al., PNAS, 99, 2609,

28 Effect of Geo-Engineering on Arctic O 3 Loss Cold Winter Moderately Cold Winter Enhancement of stratospheric aerosols due to geo-engineering risks: a) future Arctic Ozone Hole in cold winters b) 30 to 70 year delay in the recovery of the Antarctic ozone hole Tilmes et al., Science,

29 Geo-engineering of climate garnered lots of renewed attention with the publication, in August 2006, of an article entitled: Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolved a Policy Dilemma? by Paul J. Crutzen : Climatic Change, 77, , 2006 Ozone depletion Global column O 3 2.5% following eruption of Mt. Pinatubo Compensating for CO 2 doubling would lead to less ozone loss than followed Pinatubo Stratospheric chlorine is declining, so enhanced O 3 loss less worrisome in the future National Academy of Sciences: There s something else to consider For the injection of sulfate aerosols, an additional concern exists: the potential for increased concentrations of stratospheric aerosols to enhance the ability of residual chlorine, left from the legacy of chlorofluorocarbon use, to damage the ozone layer, especially in the early spring months at high latitudes. A sudden increase in stratospheric sulfate aerosol could strongly enhance chemical loss of stratospheric polar ozone for several decades, especially in the Arctic (Tilmes et al., 2008: 89 citations) 29

30 Analysis of Surface Temperature Canty et al., ACPD submitted 20 July,

31 Weighted Multiple Linear Regression T MDL i = (1+ γ) (GHG RF i ) + (NAA RF i) + C o + C 1 SOD i 6 + C 2 TSI i + C 3 ENSO i + C 4 AMO i + C 5 PDO i + C 6 IOD i Q OCEAN i Anthropogenic forcing term: accounts for greenhouse gas (GHG) radiative forcing and net anthropogenic aerosol (NAA) radiative forcing Canty et al., ACPD submitted 20 July,

32 Weighted Multiple Linear Regression T MDL i = (1+ γ) (GHG RF i ) + (NAA RF i) + C o + C 1 SOD i 6 + C 2 TSI i + C 3 ENSO i + C 4 AMO i + C 5 PDO i + C 6 IOD i Q OCEAN i Multiple linear regression: determines the contribution to temperature record from various climate proxies. Canty et al., ACPD submitted 20 July,

33 Weighted Multiple Linear Regression T MDL i = (1+ γ) (GHG RF i ) + (NAA RF i) + C o + C 1 SOD i 6 + C 2 TSI i + C 3 ENSO i + C 4 AMO i + C 5 PDO i + C 6 IOD i Q OCEAN i Export of energy into the ocean Canty et al., ACPD submitted 20 July,

34 Analysis of Surface Temperature Canty et al., ACPD submitted 20 July, 2012 Lean and Rind, GRL,

35 Analysis of Surface Temperature Our model includes a climate sensitivity parameter that accounts for feedbacks due to water vapor, clouds, albedo, etc.. Also, accounts for energy flow to the ocean Canty et al., ACPD submitted 20 July,

36 Analysis of Surface Temperature Our model includes a climate sensitivity parameter that accounts for feedbacks due to water vapor, clouds, albedo, etc.. Also, accounts for energy flow to the ocean We can include other climate proxies in our regression analysis, such as the Pacific Decadal Oscillation (PDO), Indian Ocean Dipole (IOD), and the Atlantic Multidecadal Oscillation (AMO) Canty et al., ACPD submitted 20 July,

37 Atlantic Meridional Overturning Circulation (AMOC) 37

38 Atlantic Multidecadal Oscillation (AMO) The Atlantic multidecadal oscillation occurs on a year cycle (Schelsinger and Ramunkutty, 1994). Different theories as to what drive this behavior: May be due to the interplay between AMOC and the export of sea ice through the Fram Strait (Dima and Lohmann, 2007). Dima and Lohmann,

39 Atlantic Multidecadal Oscillation (AMO) The Atlantic multidecadal oscillation occurs on a year cycle (Schelsinger and Ramunkutty, 1994). Different theories as to what drive this behavior: May be due to the interplay between AMOC and the export of sea ice through the Fram Strait (Dima and Lohmann, 2007). Could be due to forcing from anthropogenic aerosols (Booth et al., 2012). Booth et al.,

40 Atlantic Multidecadal Oscillation Canty et al., ACPD submitted 20 July,

41 Analysis of Surface Temperature Canty et al., ACPD submitted 20 July,

42 Analysis of Surface Temperature Canty et al., ACPD submitted 20 July,

43 Analysis of Surface Temperature Canty et al., ACPD submitted 20 July,

44 Analysis of Surface Temperature Canty et al., ACPD submitted 20 July,

45 SOD vs AMO 45

46 T vs SOD 46

47 Analysis of Atmospheric Temperature Canty et al., ACPD submitted 20 July,

48 Analysis of Atmospheric Temperature Canty et al., ACPD submitted 20 July,

49 Analysis of Atmospheric Temperature Canty et al., ACPD submitted 20 July,

50 Analysis of Atmospheric Temperature Canty et al., ACPD submitted 20 July,

51 SOD GISS Surface Temperature Record T PINATUBO NO AMO Had3 SST Had3 LIN Had3 AF CRU4, global GISS, global NCDC, global CRU4, land GISS, land NCDC, land BEG, land Lower Atmos. Temperature Record MSU, global MSU, land Canty et al., ACPD submitted 20 July,

52 Overall Implications for Geo-engineering Temperature records indicate atmosphere cooled after major eruptions: The timing of stratospheric optical depth (SOD) and North Atlantic SST anomalies suggest changes in ocean circulation preceded the four major volcanic eruptions that have occurred since Data record suggests ocean circulation has affected prior estimates of volcanic cooling Geo-engineering schemes based on input of sulfate aerosols into the stratosphere must be re-calibrated 0.5 cooling from Pinatubo based on Atmospheric temperature record not Surface temperature record Canty et al., ACPD submitted 20 July,

53 Overall Implications for Geo-engineering Temperature records indicate atmosphere cooled after major eruptions: The timing of stratospheric optical depth (SOD) and North Atlantic SST anomalies suggest changes in ocean circulation preceded the four major volcanic eruptions that have occurred since If geo-engineering via anthropogenic release of sulfate aerosols is Data still on record the suggests table the ocean question circulation remains. has affected prior estimates of volcanic cooling Who controls the thermostat? Geo-engineering schemes based on input of sulfate aerosols into the stratosphere must be re-calibrated 0.5 cooling from Pinatubo based on Atmospheric temperature record not Surface temperature record Canty et al., ACPD submitted 20 July,

54 Overall Implications for Geo-engineering Temperature records indicate atmosphere cooled after major eruptions: The timing of stratospheric optical depth (SOD) and North Atlantic SST anomalies suggest changes in ocean circulation preceded the four major volcanic eruptions that have occurred since If geo-engineering via anthropogenic release of sulfate aerosols is Data still on record the suggests table the ocean question circulation remains. has affected prior estimates of volcanic cooling Who controls the thermostat? Geo-engineering schemes based on input of sulfate aerosols into the stratosphere must be re-calibrated 0.5 cooling from Pinatubo based on Atmospheric temperature record not Surface temperature record Canty et al., ACPD submitted 20 July,