1 MET 112 Global Climate Change MET 112 Global Climate Change - Lecture 11 Radiative Forcing Eugene Cordero San Jose State University Outline  GHG/Aerosols  Radiative Forcing  Activity

2 MET 112 Global Climate Change Climate Change: how much and in what direction?  We have studied the various factors that contribute to climate change.    It would be helpful if we could develop a tool for measuring the strength of the various warming and cooling factors. 

3 MET 112 Global Climate Change Climate Change: how much and in what direction?  We have studied the various factors that contribute to climate change.  Some of these contribute to warming the climate  Some of these contribute to cooling the climate  It would be helpful if we could develop a tool for measuring the strength of the various warming and cooling factors.  The Radiative Forcing calculation is a tool for measuring how climate will change due to a particular forcing mechanism.

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5 Anthropogenic Forcing  Without doubt, humans have altered the radiative balance of the Earth system. The changes can be partitioned into the following categories: –Enhanced greenhouse gases  CO 2, CH 4, N 2 O, CFC’s –Ozone  –Aerosols (Natural and Anthropogenic)  Sulfate  Carbon  –Land Use Changes

6 MET 112 Global Climate Change Anthropogenic Forcing  Without doubt, humans have altered the radiative balance of the Earth system. The changes can be partitioned into the following categories: –Enhanced greenhouse gases  CO 2, CH 4, N 2 O, CFC’s –Ozone  Tropospheric  Stratospheric –Aerosols (Natural and Anthropogenic)  Sulfate  Carbon  Biomass burning (black carbon) –Land Use Changes First part of today’s lecture

7 MET 112 Global Climate Change Atmospheric Aerosols  Microscopic liquid/solid particles –Natural sources - examples  Volcanoes (sulfur)  Fires, dust –Dust, sulfate particles reflect incoming sunlight: ___________________ –Smoky soot absorb incoming sunlight: ____________________

8 MET 112 Global Climate Change Atmospheric Aerosols  Microscopic liquid/solid particles –Natural sources - examples:  Volcanoes (sulfur)  Fires, dust –Dust, sulfate particles reflect incoming sunlight: ___________________ –Smoky soot absorb incoming sunlight: ____________________ Cool atmosphere warm atmosphere

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11 MET 112 Global Climate Change Aerosols (II)  Natural sources include: – Dust, sea salt and volcanic emissions  Anthropogenic sources include –  Biomass burning: –  Aerosols have ‘short’ relative lifetimes –They can ‘float’ around for a few days to a week or two.  Aerosols affect the Earth’s energy balance by –  Cooling influence is stronger

12 MET 112 Global Climate Change Aerosols (II)  Natural sources include: – Dust, sea salt and volcanic emissions  Anthropogenic sources include –Automobiles, factories and biomass burning.  Biomass burning: –Anthropogenic portion: burning of large forests for agriculture  Aerosols have ‘short’ relative lifetimes –They can ‘float’ around for a few days to a week or two.  Aerosols affect the Earth’s energy balance by – reflecting incoming energy and/or –absorbing incoming shortwave and longwave radiation.  Cooling influence is stronger

13 MET 112 Global Climate Change Aerosols (III)  There are three major types of aerosols –Sulfate aerosols –Black carbon aerosols –Organic carbon aerosols

14 MET 112 Global Climate Change Aerosols (III)  There are three major types of aerosols –Sulfate aerosols –Black carbon aerosols –Organic carbon aerosols –All have been increasing in concentration over the last 150 years – the industrial revolution.

15 MET 112 Global Climate Change Aerosol Observations from NASA Satellite

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18 MET 112 Global Climate Change Sulfate Aerosols  Natural source: volcanoes  Anthropogenic sources: burning of fossil fuels   Example: SO 2 (sulfur dioxide- –  Sulfate aerosols increasing globally   Total effect on Earth’s energy budget – –Radiative Forcing:

19 MET 112 Global Climate Change Sulfate Aerosols  Natural source: volcanoes  Anthropogenic sources: burning of fossil fuels  90% of sulfur aerosols are anthropogenic  Example: SO 2 (sulfur dioxide- –From coal combustion  Sulfate aerosols increasing globally  Sulfate aerosols reflect incoming solar radiation.  Total effect on Earth’s energy budget –Cooling –Radiative Forcing: negative

20 MET 112 Global Climate Change Black Carbon (Aerosols)  Natural source –  Anthropogenic source –incomplete combustion from coal and diesel engines; biomass burning   Black carbon absorbs solar radiation –  Potentially harmful if inhaled.  Total effect on Earth’s energy budget – –Radiative Forcing:  Radiative Forcing: positive

21 MET 112 Global Climate Change Black Carbon (Aerosols)  Natural source: –Natural biomass burning  Anthropogenic source –incomplete combustion from coal and diesel engines; biomass burning  Also know as - ‘Elemental Carbon’ or ‘soot’  Black carbon absorbs solar radiation –It’s black so has a low albedo.  Potentially harmful if inhaled.  Total effect on Earth’s energy budget –Warming –Radiative Forcing: positive

22 MET 112 Global Climate Change Organic Carbon (Aerosols)  Natural source –  Anthropogenic source –Burning fuel –Biomass burning  Produced as a result of incomplete combustion.   Total effect on Earth’s energy budget – –Radiative Forcing:

23 MET 112 Global Climate Change Organic Carbon (Aerosols)  Natural source –Natural biomass burning  Anthropogenic source –Burning fuel –Biomass burning  Produced as a result of incomplete combustion.  These aerosols are reflective  Total effect on Earth’s energy budget –Cooling –Radiative Forcing: negative

24 MET 112 Global Climate Change Indirect Effect due to aerosols (I)   Recall how clouds form – –This processes requires ‘cloud condensation nuclei’ –Examples of cloud condensation nuclei  Dust, salt, smoke (all of which are natural aerosols)  So, aerosols (with both natural and anthropogenic origin) –

25 MET 112 Global Climate Change Indirect Effect due to aerosols (I)  Certain aerosols may enhance cloud production and character  Recall how clouds form – –This processes requires ‘cloud condensation nuclei’ –Examples of cloud condensation nuclei  Dust, salt, smoke (all of which are natural aerosols)  So, aerosols (with both natural and anthropogenic origin) –

26 MET 112 Global Climate Change Indirect Effect due to aerosols (I)  Certain aerosols may enhance cloud production and character  Recall how clouds form –Water vapor condenses to liquid water –This processes requires ‘cloud condensation nuclei’ –Examples of cloud condensation nuclei  Dust, salt, smoke (all of which are natural aerosols)  So, aerosols (with both natural and anthropogenic origin) –may serve as cloud condensation nuclei.

27 MET 112 Global Climate Change Indirect Effect due to aerosols (II)  More cloud condensation nuclei –  The question then is how would clouds change –Current understanding is that  This idea of enhanced cloud formation by increases in aerosols is termed –  Understanding of these processes is currently incomplete. –But model results suggest more low clouds and thus –Radiative Forcing:  Total effect on Earth’s energy budget – –Cirrus cloud (high clouds) production possible, but still uncertain how important.

28 MET 112 Global Climate Change Indirect Effect due to aerosols (II)  More cloud condensation nuclei – would enhance cloud production  The question then is how would clouds change –Current understanding is that This processes would increase cloud albedo  This idea of enhanced cloud formation by increases in aerosols is termed –The ‘indirect effect’ of aerosols  Understanding of these processes is currently incomplete. –But model results suggest more low clouds and thus  Total effect on Earth’s energy budget –Cooling –Radiative Forcing: negative –Cirrus cloud (high clouds) production possible, but still uncertain how important.

Weather, Aerosols and Climate – film clip

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Over the last 250 years, CO2 concentrations have increased. The earth’s surface would therefore 1.Receive more energy resulting in warming 2.Receive less energy resulting in cooling 3.Stay the same

Over the last 250 years, CH4 concentrations have increased. The earth’s surface would therefore 1.Receive more energy resulting in warming 2.Receive less energy resulting in cooling 3.Stay the same

Over the last 250 years, sulfate aerosol concentrations have increased. The earth’s surface would therefore 1.Receive more energy resulting in warming 2.Receive less energy resulting in cooling 3.Stay the same

Over the last 250 years, CFC concentrations have increased. The earth’s surface would therefore 1.Receive more energy resulting in warming 2.Receive less energy resulting in cooling 3.Stay the same

Over the last 250 years, black carbon aerosol concentrations have increased. The earth’s surface would therefore 1.Receive more energy resulting in warming 2.Receive less energy resulting in cooling 3.Stay the same

Over the last 250 years, the earth’s albedo has changed as a result of deforestation. The earth’s surface would therefore 1.Receive more energy resulting in warming 2.Receive less energy resulting in cooling 3.Stay the same

Over the last 250 years, organic carbon aerosol concentrations have increased. The earth’s surface would therefore 1.Receive more energy resulting in warming 2.Receive less energy resulting in cooling 3.Stay the same

Over the last 250 years, the amount of low clouds in the atmosphere has increased. The earth’s surface would therefore 1.Receive more energy resulting in warming 2.Receive less energy resulting in cooling 3.Stay the same

Over the last 250 years, the intensity of the sun’s incoming radiation has increased. The earth’s surface would therefore 1.Receive more energy resulting in warming 2.Receive less energy resulting in cooling 3.Stay the same

Over the last 250 years, aircraft induced high clouds have increased. The earth’s surface would therefore 1.Receive more energy resulting in warming 2.Receive less energy resulting in cooling 3.Stay the same

Radiative Forcing: Positive Values: Negative Values:

Radiative Forcing: Positive Values: Warming the Earth’s surface Negative Values: Cooling the Earth’s Surface

43 MET 112 Global Climate Change Radiative Forcing  A change imposed upon the climate system which modifies the Earth’s energy (radiative) balance.  Radiative forcing is usually given in units of –  Positive values of radiative forcing –  Negative values of radiative forcing –

44 MET 112 Global Climate Change Radiative Forcing  A change imposed upon the climate system which modifies the Earth’s energy (radiative) balance.  Radiative forcing is usually given in units of –watts per square meter (W/m 2 ),  Positive values of radiative forcing –contribute to heating of the surface,  Negative values of radiative forcing –Contribute to cooling of surface.

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46 MET 112 Global Climate Change Radiative Forcing  Examples of radiative forcing mechanisms include – – –Changes in atmospheric composition   

47 MET 112 Global Climate Change Radiative Forcing  Examples of radiative forcing mechanisms include –Changes in solar intensity –Volcanic activity –Changes in atmospheric composition  CO 2  Aerosols  Ozone –Changes in land surfaces

48 MET 112 Global Climate Change Radiative Forcing  Changes in these mechanisms –  The magnitude of the radiative forcing determine how strong the effect is.  Radiative forcing is computed by comparing –

49 MET 112 Global Climate Change Radiative Forcing  Changes in these mechanisms –produce changes to the earth energy budget.  The magnitude of the radiative forcing determine how strong the effect is.  Radiative forcing is computed by comparing –Pre-industrial energy balance (1750) with today’s energy balance (2000)

50 MET 112 Global Climate Change Enhanced Greenhouse Gases  Greenhouse gas concentrations have increased over the last 150 years dramatically  The main anthropogenic contribution to greenhouse gases concentrations include:  CO 2, CH 4, N 2 O, CFC’s (Halons)  Increases in greenhouse gas concentrations are well observed 

51 MET 112 Global Climate Change Enhanced Greenhouse Gases  Greenhouse gas concentrations have increased over the last 150 years dramatically  The main anthropogenic contribution to greenhouse gases concentrations include:  CO 2, CH 4, N 2 O, CFC’s (Halons)  Increases in greenhouse gas concentrations are well observed  Radiative Forcing: positive

52 MET 112 Global Climate Change Ozone  Ozone exists in upper atmosphere – –Ozone layer protects the earth from harmful UV radiation – –Stratospheric ozone levels have been declining over last 20 years (ozone depletion) –  Ozone exists in lower atmosphere – –Tropospheric ozone levels have increased over last 20 years. –

53 MET 112 Global Climate Change Ozone  Ozone exists in upper atmosphere –Ozone layer (stratospheric ozone) –Ozone layer protects the earth from harmful UV radiation –Ozone layer responsible for heating the stratosphere –Stratospheric ozone levels have been declining over last 20 years (ozone depletion) –Radiative Forcing: negative  Ozone exists in lower atmosphere – Tropospheric ozone is another word for ‘smog’ –Tropospheric ozone levels have increased over last 50 years. –Radiative Forcing: positive

54 MET 112 Global Climate Change Land Use Change  Changes in the land use have contributed to –  Deforestation has been largest contributor  High latitudes have been most affected –Pre Industrial: Snow covered forests (low albedo) –  Again, large uncertainties remain 

55 MET 112 Global Climate Change Land Use Change  Changes in the land use have contributed to –Albedo changes  Deforestation has been largest contributor  High latitudes have been most affected –Pre Industrial: Snow covered forests (low albedo) –Current: Open snow covered areas (high albedo)  Again, large uncertainties remain  Radiative Forcing: negative

Radiative Forcing from the IPCC

Radiative Forcing from the IPCC What does this part of the diagram mean?

Radiative Forcing from the IPCC What does this part of the diagram mean? Increases in greenhouse gases (CO 2, CH 4, N 2 O and Halocarbons) between 1750 through today (2000) have caused a 2.4 Watts per meter squared increase in the earth’s radiation budget. This by itself would warm the earth’s surface.

60 MET 112 Global Climate Change Radiative Forcing from the IPCC What does this plot mean? Increases in greenhouse gases (CO 2, CH 4, N 2 O and Halocarbons) between 1750 through today (2000) have caused a 2.4 Watts per meter squared increase in the earth’s radiation budget. This by itself would warm the earth’s surface. Radiative forcing = 2.4  0.2 or between 2.2 and 2.6

Example  Imagine you and your partner get offers to work for a new progressive company. They use a sliding pay scale. You will get paid: $35,000  5,000 depending on your performance and your partner will get paid $75,000  100,000. Calculate your total average salary (mean) and the range of possible salaries. –The total (combined) salary is: –Your salary ranges from –Your partner’s salary ranges from  Maximum possible salary:  Minimum possible salary: 

Example  Imagine you and your partner get offers to work for a new progressive company. They use a sliding pay scale. You will get paid: $35,000  5,000 depending on your performance and your partner will get paid $75,000  100,000. Calculate you are your partner’s total average salary and the range of possible salaries. –The total (combined) salary is: = $110,000 –Your salary ranges from $30,000 to 40,000 –Your partner’s salary ranges from $ -25,000 to 175,000  Maximum possible salary: $215,000  Minimum possible salary: $5,000  So, the total salary is $110,000  105,000  Big uncertainity!

63 MET 112 Global Climate Change Terms in the radiative forcing diagram  Term 1: Increases in CO 2, CH 4, N 2 O and CFCs –  Term 2: Decreases in upper atmospheric ozone (ozone depletion) –  Term 3: Increases in lower atmosphere ozone –  Term 4: Increases in sulfate aerosols –  Term 5: Increases in black carbon –

64 MET 112 Global Climate Change Terms in the radiative forcing diagram  Term 1: Increases in CO 2, CH 4, N 2 O and CFCs – producing warming (positive)  Term 2: Decreases in upper atmospheric ozone (ozone depletion) –provide less heating of upper atmosphere (negative)  Term 3: Increases in lower atmosphere ozone –produce warming (positive)  Term 4: Increases in sulfate aerosols –produce cooling (negative)  Term 5: Increases in black carbon –produce warming (positive)

65 MET 112 Global Climate Change Terms in the radiative forcing diagram  Term 6: Increases in organic carbon aerosol –  Term 7: Increases in biomass burning aerosols –  Term 8: Increases in mineral dust –  Term 9: Increases in aerosols alter cloud properties (more low level clouds) –

66 MET 112 Global Climate Change Terms in the radiative forcing diagram  Term 6: Increases in organic carbon aerosol –produce cooling (negative)  Term 7: Increases in biomass burning aerosols –produce cooling (negative)  Term 8: Increases in mineral dust –could warm or cool (unknown at present)  Term 9: Increases in aerosols alter cloud properties (more low level clouds) –produce cooling (negative)

67 MET 112 Global Climate Change Terms in the radiative forcing diagram  Term 10-11: Increases in aircraft induced high clouds (contrails and cirrus clouds) –  Term 12: Increases in the removal of forests (land use) which cause albedo changes –  Term 13: Increases in the strength of the sun –

68 MET 112 Global Climate Change Terms in the radiative forcing diagram  Term 10-11: Increases in aircraft induced high clouds (contrails and cirrus clouds) –produce warming (positive)  Term 12: Increases in the removal of forests (land use) which cause albedo changes –produce cooling (negative)  Term 13: Increases in the strength of the sun –produce warming (positive)

69 MET 112 Global Climate Change Radiative Forcing example  Imagine that the only two anthropogenic forcing terms changing the climate are: –Greenhouse Gases –Ozone Depletion  Calculate the radiative forcing just due to those two terms including the uncertainties:

70 MET 112 Global Climate Change Radiative Forcing example  Imagine that the only two radiative forcing terms are changing the climate are: –Greenhouse Gases –Ozone Depletion  Calculate the radiative forcing just due to those two terms including the uncertainties: 2.4  0.2 (2.2 to 2.6) -0.1  0.1 (0 to -0.2) Add the two forcing terms (Mean): (-0.1) = 2.3 Calculate range of values = 2.6; 2.2+(-0.2)=2.0 Mean = 2.3 Range of values between (2.0 to 2.6) Positive Forcing!

71 MET 112 Global Climate Change Uncertainty or Range of values possible  To calculate the range of possible values: –Add the most positive radiative forcing –Add the most negative radiative forcing  This will determine the range of possible values.

72 MET 112 Global Climate Change Activity 1.Calculate the total mean radiative forcing from the provided figure of individual radiative forcing from the IPCC. You may omit the mineral dust and aviation terms. Please show your work! 2.Calculate the total range of possible values from the above calculation 3.What conclusions does the total mean radiative forcing tell us about how the climate has changed? 4.How does the range of values (or uncertainties) affect our above conclusions?

73 MET 112 Global Climate Change Q1: What is the total mean radiative forcing 1.Between -5 and -3 W/m 2 2.Between -3.0 and -1.0 W/m 2 3.Between -2.0 and -1.0 W/m 2 4.Between -1.0 and -0.1 W/m 2 5.Between 0 and 1.0 W/m 2 6.Between 1.0 and 3.0 W/m 2 7.Between 3 and 5 W/m 2 8.Between 5 and 9 W/m 2

74 MET 112 Global Climate Change Q2: What is the maximum radiative forcing 1.Between -5 and -3 W/m 2 2.Between -3.0 and -1.0 W/m 2 3.Between -1.0 and -0.1 W/m 2 4.Between 0 and 1.0 W/m 2 5.Between 1.0 and 2.0 W/m 2 6.Between 2 and 4 W/m 2 7.Between 4 and 6 W/m 2

75 MET 112 Global Climate Change Q2: What is the minimum radiative forcing 1.Between -5 and -3 W/m 2 2.Between -3.0 and -1.0 W/m 2 3.Between -1.0 and -0.1 W/m 2 4.Between 0 and 1.0 W/m 2 5.Between 1.0 and 2.0 W/m 2 6.Between 2 and 4 W/m 2 7.Between 4 and 6 W/m 2

76 MET 112 Global Climate Change Q3: What conclusions does the mean forcing tell us 1.Warming forcing outweighs cooling 2.Cooling forcing outweighs warming 3.Human induced warming is much stronger than naturally forced warming. 4.Both 1 and 3 5.Both 2 and 3

77 MET 112 Global Climate Change Q4: What conclusions does the range of radiative forcing tell us 1.The warming forcing is more certain than the cooling. 2.The cooling forcing is more certain than the warming. 3.The earth should be warming, but by how much is difficult to say because of the uncertainty of the cooling factors. 4.The cooling is stronger than the warming and thus the earth should cool. 5.Both 1 and 3 6.Both 1 and 4 7.Both 2 and 3 8.Both 2 and 4

End of Lecture

79 MET 112 Global Climate Change Uncertainties  Although you can examine the radiative forcing, you must also consider the uncertainties of each estimate!  The uncertainties in our understanding of the climate system make definite predictions more challenging.  However, estimates of uncertainties also provide valuable information!

Radiative Forcing from the IPCC TermMeanLowHigh CO2 etc Strat o Trop O Sulfate Black Carbon Organic Carbon Biomass burn Tropo indirect Solar Total

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82 MET 112 Global Climate Change Energy Balance  The Earth’s atmosphere and surface are in radiative balance: –Energy coming in = energy going out  This balance is true everywhere: –At the earth’s surface –At the top of the atmosphere –Within the atmosphere

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86 MET 112 Global Climate Change Activity 12 In the IPCC estimate of the Earth’s energy balance, show how the earth’s energy balance is maintained at the: A) Top of the atmosphere B) Within the atmosphere C) Earth’s surface Be sure to indicate how the energy is balanced (using numbers) and where that energy comes from at each level.

87 MET 112 Global Climate Change What is the energy balance at the top of the earth’s atmosphere? Wm -2 in, 235 Wm -2 out Wm -2 in, 342 Wm -2 out Wm -2 in, 235 Wm -2 out 4.77 Wm -2 in 77 Wm -2 out

88 MET 112 Global Climate Change What is the energy balance at the Earth’s surface? Wm -2 in, 390 Wm -2 out Wm -2 in, 168 Wm -2 out Wm -2 in, 522 Wm -2 out Wm -2 in 492 Wm -2 out 0 of 66

89 MET 112 Global Climate Change What is the energy balance within the atmosphere? Wm -2 in, 596 Wm -2 out Wm -2 in, 519 Wm -2 out Wm -2 in, 350 Wm -2 out Wm -2 in 492 Wm -2 out 0 of 66