Physical Science Basis of Climate Change: IPCC 2007 Emilia K. Jin Chapter 7: Couplings Between...

Physical Science Basis of Climate Change: IPCC 2007

Emilia K. JinEmilia K. Jin

Chapter 7: Couplings Between Changes in the Climate System and Biogeochemistry

ContentsContents

1. Feedbacks

2. Global Carbon - Climate System

3. Land - Climate Interaction

4. Ocean - Climate Interaction

5. Reactive Gases

6. Aerosol

Bottom Line: Carbon – Climate feedbacks are critically important for predicting future climate change, but the more we learn the more we realize that we do not understand…

ContentsContents

1. Feedbacks




5. Reactive Gases

6. Aerosol

Couplings Between Changes Couplings Between Changes in thein the Climate System and BiogeochemistryClimate System and Biogeochemistry

Complex connected physical, chemical and biological processes occurring in the atmosphere, land and ocean.

Complex connected physical, chemical and biological processes occurring in the atmosphere, land and ocean.

Earth’s ClimateEarth’s Climate

• Natural and anthropogenic emissions of gases and aerosols• Transport at a variety of scales, chemical and microphysical transformations• Wet scavenging and surface uptake by the land and terrestrial ecosystems• Wet scavenging and surface uptake by the ocean and its ecosystems.

• Natural and anthropogenic emissions of gases and aerosols• Transport at a variety of scales, chemical and microphysical transformations• Wet scavenging and surface uptake by the land and terrestrial ecosystems• Wet scavenging and surface uptake by the ocean and its ecosystems.

BBiogeochemical cyclingiogeochemical cycling

Biophysical state of the Earth’s surface: LLGHGs, CO2, CH4, N2O, ozone, and aerosol particles.

Biophysical state of the Earth’s surface: LLGHGs, CO2, CH4, N2O, ozone, and aerosol particles.

RRadiativeadiative properties properties of the atmosphereof the atmosphere

CComposition of omposition of the atmospherethe atmosphere

Nonlinear interactions between/within the different components of the Earth system

To identify the major biogeochemical feedbacks of significance to the climate system, and to assess current knowledge of their magnitudes and trends. Examine the relationships between the physical climate system and the land surface, the carbon cycle, chemically reactive atmospheric gases and aerosol particles. There are large uncertainties to provide a simple quantitative description.

Radiative Forcing Components and Radiative Forcing Components and Their Feedbacks to the Climate SystemTheir Feedbacks to the Climate System

• Largest forecers are CO2, CH4, aerosols, ozone, and surface albedo (reflectivity).

• They all involve potential feedbacks to the climate system, usually through biogeochemistry.

• Nonlinear interactions between the climate and biogeochemical systems could amplify or attenuate the disturbances produced by human activities.

Positive vs. Negative Positive vs. Negative FeedbackFeedback

1. Something triggers a small system change

2. The system responds to the change

3. Feedback

• Positive Feedback: The response accelerates the original change

• Negative Feedback: The response damps the original change

Time

Tem

per

atu

re

If no feedbacks present

With positive feedbacks

Effect of Positive Effect of Positive Feedback (1)Feedback (1)

Effect of Positive Feedback Effect of Positive Feedback (2)(2)

Time

Tem

per

atu

re

If no feedbacks present

With positive feedbacks

The Need for Negative The Need for Negative FeedbacksFeedbacks

• Positive feedbacks are destabilizing - they tend to drive the system away from equilibrium

• Negative feedbacks are required to restore equilibrium

A System Without Negative A System Without Negative FeedbacksFeedbacks

Time

Tem

per

atu

re

Catastrophic Warming!

Example “Runaway Greenhouse Effect”, T H2O T

The Way Physical Systems Usually BehaveThe Way Physical Systems Usually Behave

Time

Tem

per

atu

r e

Warming Accelerating

Warming Decelerating

Feedbacks - SummaryFeedbacks - Summary

• Positive feedbacks tend to increase the amplitude of the system response

• Negative feedbacks tend to reduce the amplitude of the system response

Feedbacks in the Feedbacks in the BiosphereBiosphere

1. The plankton multiplier in the ocean (positive)

(Colder Stronger Ocean Biological Pump Remove ATM CO2)

2. Carbon dioxide fertilization, plant growth (negative)

3. Effect of higher temperatures on respiration (positive)

4. Reduction of forest growth because of climate change (positive)

5. Increased greenhouse gases due to increase of fires (positive)

6. Release of methane from wetland and permafrost (positive)

Feedbacks in the Climate Feedbacks in the Climate SystemSystem

• Water vapor feedback

• Cloud-radiation feedback

• Ice-albedo feedback

• Climate-Carbon Cycle feedback

Ice-Albedo Feedback Ice-Albedo Feedback (1)(1)

Cooling

Albedo Increases

Absorption of sunlight

decreases

Ice Increases

Ice-Albedo Feedback Ice-Albedo Feedback (2)(2)

Warming

Albedo Decreases

Absorption of sunlight

increases

Ice Decreases

Water Vapor Feedback Water Vapor Feedback (1)(1)

Warming

Evaporation from the Oceans Increases

Atmospheric Water Vapor Increases

Stronger Greenhouse Effect

Water Vapor Feedback Water Vapor Feedback (2)(2)

Cooling

Evaporation from the Oceans Decreases

Atmospheric Water Vapor Decreases

Weaker Greenhouse Effect

Water Vapor Feedback is Positive

1. Equilibrium Climate Sensitivity (ECS) and Transient Climate Response (TCR)

• Definitions

• Model ECS and TCR—the role of feedbacks

2. Detection and Attribution

• Detection and Attribution of What?

• Modeling with and without anthropogenic forcing

3. Understanding?

Understanding and Attributing Climate ChangeUnderstanding and Attributing Climate Change

Definition: The ECS is the full equilibrium surface temperature response to a doubling of CO2

Definition: The TCR is the surface temperature response at CO2 doubling for a 1%/yr increase of CO2 (i.e. at year 70)

a. ECS and TCR are basically model concepts

b. TCR < ECS

c. ECS is a measure of the feedbacks in the system:

Recall:

Equilibrium Climate Sensitivity (ECS) and Equilibrium Climate Sensitivity (ECS) and

Transient Climate Response (TCR)Transient Climate Response (TCR)

J. Shukla, T. DelSole, M. Fennessy, J. Kinter and D. Paolino

Geophys. Research Letters, 33, doi10.1029/2005GL025579, 2006

Climate Model Fidelity and Projections of Climate ChangeClimate Model Fidelity and Projections of Climate Change

ContentsContents

1. Feedbacks




5. Reactive Gases

6. Aerosol

Carbon DioxideCarbon Dioxide

Raupachet al., 2007 PNAS

Carbon DioxideCarbon Dioxide

Raupachet al., in press. PNAS

Fraction of the CO2 emitted by human activities Fraction of the CO2 emitted by human activities which remains in the atmosphere which remains in the atmosphere

airborne fraction = atm / (fossil fuel + cement + land use emissions)

Carbon Dioxide Carbon Dioxide

• The rate of increase of CO2 emissions from fossil fuels has been increasing (top line)

• The rate of increase of atmospheric CO2 has been increasing Bars : yearly Solid lines : 5-year means(Black for SCRIPPS Red for NOAA)

• Less so since 1990

* 2.1 Gt-C of CO2 is equivalent to 1 ppm concentration in the atmosphere

Carbon Dioxide Carbon Dioxide

CO2 Concentration Remained in the ATM.

Are there changes in the efficiency Are there changes in the efficiency of the land and/or ocean sinks for CO2 ? of the land and/or ocean sinks for CO2 ?

Climate Change ScenariosClimate Change Scenarios

The problem of projecting the future climate has many aspects. One way to make a prediction is to predict the concentration of GHG in the future and apply that future concentration to a climate system model to determine how the climate system will respond.

There are three critical issues:

1.The projection of future GHG concentrations depends on the future emissions 2.The future concentration of GHG depend on the uptake of emitted GHG by various parts of the climate system3.The simulated response of the future climate system depends on how well the climate system model simulates the current climate

For issue #1, the IPCC makes use of the

SRES (Special Report on Emission Scenarios)http://www.grida.no/publications/other/ipcc_sr/?src=/climate/ipcc/emission/

Climate Change Scenarios, Predicting Climate Change of the Climate Change Scenarios, Predicting Climate Change of the

Future and the IPCC AssessmentsFuture and the IPCC Assessments

http://www.grida.no/publications/other/ipcc_sr/?src=/climate/ipcc/emission/

The IPCC Assessments of The IPCC Assessments of ClimateClimate Change and UncertaintiesChange and Uncertainties

• The six IPCC scenarios areThe six IPCC scenarios are spline fits to projections (initialized spline fits to projections (initialized

with observations for 1990) of possiblewith observations for 1990) of possible future emissions for four future emissions for four

scenario families, A1, A2, B1, and B2, which emphasizescenario families, A1, A2, B1, and B2, which emphasize globalized globalized

vs. regionalizedvs. regionalized development on the development on the A,BA,B axis and axis and economiceconomic growth growth

vs. environmental stewardshipvs. environmental stewardship on the on the 1,21,2 axis. axis.

• Three variants of the A1Three variants of the A1 (globalized, economically oriented) (globalized, economically oriented)

scenario lead to different emissions trajectories:scenario lead to different emissions trajectories: A1FI (intensive A1FI (intensive

dependence on fossil fuels), A1T (alternative technologiesdependence on fossil fuels), A1T (alternative technologies largely largely

replace fossil fuels), and A1B (balanced energy supply betweenreplace fossil fuels), and A1B (balanced energy supply between

fossil fuels and alternatives).fossil fuels and alternatives).

The IPCC AR4

Different scenarios:

A1. The A1 storyline and scenario family describes a future world of very rapid economic growth, global population that peaks in mid-

century and declines thereafter, and the rapid introduction of new and more efficient technologies. Major underlying themes are

convergence among regions, capacity building and increased cultural and social interactions, with a substantial reduction in regional

differences in per capita income. The A1 scenario family develops into three groups that describe alternative directions of

technological change in the energy system. The three A1 groups are distinguished by their technological emphasis: fossil intensive

(A1FI), non-fossil energy sources (A1T), or a balance across all sources (A1B) (where “balanced” is defined as not relying too heavily

on one particular energy source, on the assumption that similar improvement rates apply to all energy supply and end use

technologies).

A2. The A2 storyline and scenario family describes a very heterogeneous world. The underlying theme is self-reliance and

preservation of local identities. Fertility patterns across regions converge very slowly, which results in continuously increasing

population. Economic development is primarily regionally oriented and per capita economic growth and technological change more

fragmented and slower than other storylines.

B1. The B1 storyline and scenario family describes a convergent world with the same global population, that peaks in mid-century and

declines thereafter, as in the A1 storyline, but with rapid change in economic structures toward a service and information economy,

with reductions in material intensity and the introduction of clean and resource efficient technologies. The emphasis is on global

solutions to economic, social and environmental sustainability, including improved equity, but without additional climate initiatives.

B2. The B2 storyline and scenario family describes a world in which the emphasis is on local solutions to economic, social and

environmental sustainability. It is a world with continuously increasing global population, at a rate lower than A2, intermediate levels

of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. While the scenario

is also oriented towards environmental protection and social equity, it focuses on local and regional levels.

The IPCC Assessments of The IPCC Assessments of

ClimateClimate Change and UncertaintiesChange and Uncertainties

IPCC SRES Emission ScenariosIPCC SRES Emission Scenarios(The Emission Scenarios of the IPCC special Report on Emission Scenarios)(The Emission Scenarios of the IPCC special Report on Emission Scenarios)

Pg (Petagram) = 1015 g = Gt (Gigaton)

The issue of “predictions”

An illustrative scenario was chosen for each of the six scenario groups A1B, A1FI, A1T, A2,

B1 and B2. All should be considered equally sound.

The SRES scenarios do not include additional climate initiatives, which means that no

scenarios are included that explicitly assume implementation of the United Nations

Framework Convention on Climate Change or the emissions targets of the Kyoto Protocol.

The IPCC Assessments of The IPCC Assessments of

ClimateClimate Change and UncertaintiesChange and Uncertainties

Projected CO2 emissions leading to stabilization of atmospheric

CO2 concentrations at different levels and the effect of uncertainty

in carbon cycle processes on calculated emissions.

Panel (a) shows the assumed trajectories of CO2 concentration

(SP scenarios)(Knutti et al., 2005)

(b) and (c) show the implied CO2 emissions, as projected with the

Bern2.5CC EMIC (Joos et al., 2001; Plattner et al., 2001).

The ranges given in (b) for each of the SP scenarios represent

effects of different model parameterizations and assumptions

illustrated for scenario SP550 in panel (c) (range for ‘CO2 +

climate’). The upper and lower bounds in (b) are indicated by the

top and bottom of the shaded areas. Alternatively, the lower

bound (where hidden) is indicated by a dashed line. Panel (c)

illustrates emission ranges and sensitivities for scenario SP550.

What is in store for the future and What is in store for the future and what has already been committedwhat has already been committed

Global warming will increase if GHGs concentration increase. Even if GHGs were kept constant at current levels, there is a “commitment” of 0.6°C of additional warming by 2100.

1.8o

C = 3.2o

F

2.8o

C = 5.0o

F

3.4o

C = 6.1o

F

CO2 Eq

850

600

4000.6

oC = 1.0

oF

WRE Stabilization Scenarios WRE Stabilization Scenarios and Permissible Emissions and Permissible Emissions

WRE: Wigley, Richels, and Edmonds (WRE 1996) used in IPCC TAR

Figure 10.22, IPCC AR4

Projected Future Warming Projected Future Warming

Figure 9.13, IPCC TAR

Multi-Model Ensemble Simulations of Multi-Model Ensemble Simulations of TT

WRE 500 Permissible Emissions and “THE GAP” WRE 500 Permissible Emissions and “THE GAP”

Coupled Climate-Carbon Cycle Models Sequester Coupled Climate-Carbon Cycle Models Sequester

A positive feedback to climate:

• Simulations indicate an additional warming of 0.1 – 1.5 °C

• Simulations indicate that stabilization of atmospheric CO2 concentration at a given level would require a greater reduction of emissions in the 21st century that in simulations without a coupled carbon cycle.

[C4MIP Results: Friedlingstein et al., 2006]

SRES Emission ScenariosSRES Emission Scenarios

Raupachet al., 2007 PNAS

ContentsContents

1. Importance of Feedbacks




5. Reactive Gases

6. Aerosol

Are there changes in the efficiency Are there changes in the efficiency of the land and/or ocean sinks for CO2 ? of the land and/or ocean sinks for CO2 ?

Coupling the Biogeochemical Cycles Coupling the Biogeochemical Cycles with the Climate Systemwith the Climate System

• It is well established that the level of atmospheric CO2, which directly influences the Earth’s temperature, depends critically on the rates of carbon uptake by the ocean and the land, which are also dependent on climate.

• Climate models that include the dynamics of the carbon cycle suggest that the overall effect of carbon-climate interactions is a positive feedback.

• Hence predicted future atmospheric CO2 concentrations are therefore higher (and consequently the climate warmer) than in models that do not include these couplings.

The present chapter assesses the current understanding of the processesinvolved and highlights the role of biogeochemical processes in the climate system.

Pre 1990s View of the Global Carbon CyclePre 1990s View of the Global Carbon Cycle

• In the early 1990s the World Ocean Circulation Experiment (WOCE), the Joint In the early 1990s the World Ocean Circulation Experiment (WOCE), the Joint Global Ocean Flux Study (JGOFS), and the NOAA/OACES program joined forces Global Ocean Flux Study (JGOFS), and the NOAA/OACES program joined forces to conduct a global survey of CO2 in the oceans.to conduct a global survey of CO2 in the oceans.

>70,000 sample locations; DIC ± 2 µmol kg-1; TA ± 4 µmol kg-1

http://cdiac.esd.ornl.gov/oceans/glodap/Glodap_home.htm

Column inventory of anthropogenic COColumn inventory of anthropogenic CO22

that has accumulated in the oceanthat has accumulated in the ocean

Carbon changes between 1800 and 1994Carbon changes between 1800 and 1994

Over the past 200 years, the ocean has been the only reservoir to consistently take up anthropogenic CO2 from the atmosphere.

Global Carbon Fluxes for 1990sGlobal Carbon Fluxes for 1990s

Largest variability & uncertainties are in carbon fluxes from land use change and 'residual terrestrial carbon sink'.

The Global Carbon Budget [Pg C]The Global Carbon Budget [Pg C]Positive values: Atmospheric increase (or ocean/land sources)Negative values: atmospheric decrease (sinks)

• First 180 years, the ocean absorbed 44% of emissions.• Last 20 years, the ocean absorbed 36% of emissions.

Sabine et al., 2004 Science

SRES Emission ScenariosSRES Emission Scenarios

• Emissions are increasing• Atmospheric increase is increasing• Inferred 'residual terrestrial sink' is highly uncertain

* 2.1 Gt-C of CO2 is equivalent to 1 ppm concentration in the atmosphere

Carbon Cycle and ClimateCarbon Cycle and Climate• Atmospheric carbon dioxide (CO2) concentration has continued to increase and is now almost 100 ppm above its pre-industrial level. The annual mean CO2 growth rate was significantly higher for the period from 2000 to 2005 (4.1 ± 0.1 GtC yr–1) than it was in the 1990s (3.2 ± 0.1 GtC yr–1). Annual emissions of CO2 from fossil fuel burning and cement production increased from a mean of 6.4 ± 0.4 GtC yr–1 in the 1990s to 7.2 ± 0.3 GtC yr–1 for 2000 to 2005.

• Carbon dioxide cycles between the atmosphere, oceans and land biosphere: Its removal from the atmosphere involves a range of processes with different time scales. About 50% of a CO2 increase will be removed from the atmosphere within 30 years, and a further 30% will be removed within a fewcenturies. The remaining 20% may stay in the atmosphere for many thousands of years.

• Improved estimates of ocean uptake of CO2 suggest little change in the ocean carbon sink of 2.2 ± 0.5 GtC yr–1 between the 1990s and the first five years of the 21st century. Models indicate that the fraction of fossil fuel and cement emissions of CO2 taken up by the ocean will decline if atmospheric CO2 continues to increase.

Carbon Cycle and ClimateCarbon Cycle and Climate

• A combination of techniques gives an estimate of the flux of CO2 to the atmosphere from land use change of 1.6 (0.5 to 2.7) GtC yr–1 for the 1990s. A revision of the Third Assessment Report (TAR) estimate for the 1980sdownwards to 1.4 (0.4 to 2.3) GtC yr–1 suggests little change between the 1980s and 1990s, and continuing uncertainty in the net CO2 emissions due to land use change.

• The first-generation coupled climate-carbon cycle models indicate that global warming will increase the fraction of anthropogenic CO2 that remains in the atmosphere. This positive climate-carbon cycle feedback leads to anadditional increase in atmospheric CO2 concentration of 20 to 224 ppm by 2100, in models run under the IPCC (2000) Special Report on Emission Scenarios (SRES) A2 emissions scenario.

ContentsContents





5. Reactive Gases

6. Aerosol

Terrestrial Ecosystems and ClimateTerrestrial Ecosystems and Climate

Balance of fluxesBalance of fluxes

Non-radiative(e.g., water cycle related processes)

Non-radiative(e.g., water cycle related processes)

Radiative(e.g. albedo)

Radiative(e.g. albedo)

Details of vegetationDetails of vegetation

Terrestrial biosphereTerrestrial biosphere

ClimateClimate

Biogeophysicalbiogeochemical

processes

High-latitudes: strong snow albedo feedbackSemiarid tropical systems: radiative and hydrological feedbacks

Vegetation cover, Biomes, Productivity,

Respiration of vegetation and soil,

Fires

Vegetation cover, Biomes, Productivity,

Respiration of vegetation and soil,

Fires

Temperature, Precipitation,

CO2, Nutrients

Photosynthetic productivity


Carbon cycle

Example: Terrestrial Ecosystems and ClimateExample: Terrestrial Ecosystems and Climate

Rainfall increase in a semi-arid system


increase


increase

Atmosphere: enhanced carbon

uptake

Ecosystem structure shift: Organic carbon

compounds in soils are respired.

Ecosystem structure shift: Organic carbon

compounds in soils are respired.

Alter the partitioning of carbon between the atmosphere and the land surface

Temp. decrease

Larger biomass of trees than herbs

and shrubs

Larger biomass of trees than herbs

and shrubs

Carbon storage increase in ecosystem.

Carbon storage increase in ecosystem.

Net flux of carbon from the atmosphere to the land surface

From boreal forest to Tundra

From boreal forest to Tundra

Rainfall decrease

Less biomass of trees

Less biomass of trees

Carbon storage decrease in ecosystem.

Carbon storage decrease in ecosystem.

Net flux of carbon from the land surface to the atmosphere

From tropical rainforest to savannah

From tropical rainforest to savannah

Feedbacks Between Changes Feedbacks Between Changes in the Land Surface and Climatein the Land Surface and Climate

1. Changes in Albedo (Reflectivity)

• Deforestation and replacement with croplands/grasslands generally raises the albedo, reflecting more incoming radiation and counteracting global warming,

- e.g. snow-covered boreal forests have lower albedo than snow-covered croplands/grasslands

• Black carbon on snow decreases albedo, increases adsorption of incoming radiation, enhancing warming.

- associated melting of snow would be a positive feedback to warming

Feedbacks Between Changes Feedbacks Between Changes in the Land Surface and Climatein the Land Surface and Climate

2. Changes in hydrological cycle / precipitation

• Changes in the land surface (vegetation, soils, water) from human activities can change rates of evaporation and affect regional climate through shifts in radiation, cloudiness and surface temperature.

- e.g. heat used to evaporate water will not be available to raise the surface temperature.

• Urban activities can change regional climate

- Replacement of vegetation with asphalt will generally increase daytime temperatures and lower humidity.

- Changing dry surfaces into vegetated surfaces by irrigation (e.g. lawns & golf courses) will generally lead to the opposite.

Changing Land Climate SystemChanging Land Climate System

• Changes in the land surface (vegetation, soils, water) resulting from human activities can affect regional climate through shifts in radiation, cloudiness and surface temperature.

• Changes in vegetation cover affect surface energy and water balances at the regional scale, from boreal to tropical forests. Models indicate increased boreal forest reduces the effects of snow albedo and causes regional warming. Observations and models of tropical forests also show effects of changing surface energy and water balance.

• The impact of land use change on the energy and water balance may be very significant for climate at regional scales over time periods of decades or longer.

ContentsContents





5. Reactive Gases

6. Aerosol

Ocean Ecosystems and ClimateOcean Ecosystems and Climate

Ocean EcosystemOcean Ecosystem

ClimateClimate

Ocean Ecosystem

Chemical composition of the atmosphere:

CO2, N2O, O2, dimethyl sulphide (DMS), sulphate

aerosol

Near-surface density stratification, ocean

circulation, temperature, salinity,

wind field, sea ice cover

Marine biota: Changes in the marine albedo and absorption

of solar radiation (biooptical heating)

Near-surface radiation budget

• Feedbacks between marine ecosystems and climate change are complex because most involve the ocean’s physical responses and feedbacks to climate change.

Examples of Ocean Ecosystems and ClimateExamples of Ocean Ecosystems and Climate

Surface Temp.

increase

Increased photosynthetic fixation of CO2

Reductions in vertical mixing and overturning

circulation: Decrease the return of required nutrients

to the surface ocean

Alter the vertical export of carbon to the deeper

ocean.

The sign of the cumulative feedback to climate of all these processes is still unclear.

Enhancedstratification

Ocean acidification due to uptake of

anthropogenic CO2

CO2

Dust deposition to the ocean surface

Increased photosynthesis

Shifts in ocean ecosystem

structure and dynamics

Alter the biological productionExport from the surface

ocean of organic carbon and calcium carbonate (CaCO3)

The supply of micronutrients, in

particular iron

Sensitivity of ocean carbon uptake to climate change

Mechanisms :

- Increasing Sea Surface Temperature (SST) decreases CO2 solubility.

- Decreased Mixing preventsthe penetration of C ant.

- Decrease in Biological Production reduces the amount of carbon transported to depth.

…..

No clear global relationship : Need to break down the responses at regional levels. Need to consider natural / anthropogenic carbon separately…..

Sensitivity of ocean carbon uptakeSensitivity of ocean carbon uptake t to climate changeo climate change

Adverse effects• biogenic calcification• hypercapnia (accumulation of CO2 in tissues)

• life cycle (hatching success, larval development, recruitment)• mortality (grazing, programmed cell death, viral infection)

Stimulating effects• phytoplankton carbon fixation• production of climate relevant trace gases• diazotrophic nitrogen fixation

Transfer of effects through the ecosystem via• competitive interaction• predator-prey interaction• symbiotic/parasitic relationships

Acclimation (gene expression, physiological)Adaptation (genetic diversity, micro-evolution)

What we knowWhat we know about the biological impacts about the biological impacts of ocean acidificationof ocean acidification

Courtesy of Dr. R. Feely

ContentsContents





5. Reactive Gases

6. Aerosol

Atmospheric Chemistry and ClimateAtmospheric Chemistry and Climate

Polluted area Radiative warmingConcentration

increase

Atmospheric oxidants (e.g. O3)

Tropospheric chemical O3 precursors (carbon monoxide, CH4, non-methane hydrocarbons, nitrogen oxides)

Stratospheric Ozone

CH4

Fossil fuel,Biomass burning,

Agricultural practicesSlight warming

Concentration increase

Manufacturedhalocarbons

Slight coolingConcentration

decrease1980s-1990s

Slow down

Late 1990s

Source strength Slight warmingConcentration

increase

Nitrous oxide

Agricultural activities Slight warmingConcentration

increase

Atmospheric Chemistry and ClimateAtmospheric Chemistry and Climate

Photochemical production of the

hydroxyl radical (OH)Increased water vapour

Destroys many atmospheric compounds

Changes in atmospheric chemical composition that could result from climate changes

• Changes in atmospheric chemical composition due to climate changes

Produce nitrogen oxidesFrequency of lightning flashes in thunderstorms

Remove soluble species from the atmosphere

Scavenging mechanisms

Intensity and frequency of convective transport events

Natural emissions of chemical compounds (e.g., biogenic hydrocarbons by the vegetation, nitrous and nitric oxide by soils, DMS from the ocean)

Other chemistry-related processes: The importance of these effects is not yet well quantified.

Surface deposition on molecules on the vegetation and soils

More frequent occurrence of stagnant air events in urban or industrial areas

Enhance the intensity of air pollution events

Biogeochemistry, Atmospheric Chemistry Biogeochemistry, Atmospheric Chemistry and Climate Changeand Climate Change

: Schematic representation of the multiple interactions between tropospheric chemical processes, biogeochemical cycles and the climate system.

• Emissions of several chemical compounds have increased substantially in response to human activities.

• As a result biogeochemical cycles have been perturbed significantly.

• Nonlinear interactions between the climate and biogeochemical systems could amplify or attenuate the disturbances produced by human activities.

Atmospheric Processes Affecting Chemical Atmospheric Processes Affecting Chemical Compounds in the AtmosphereCompounds in the Atmosphere

MethaneMethane

• Observed increases in atmospheric methane concentration are directly linked to human activities.

• Constraints on methyl chloroform observations show that there has been no significant trend in the average OH concentration, and hence in the methane removal rate.

• The slowdown in the rate of growth of atmospheric methane in recent years is attributed to the atmosphere approaching an equilibrium during a period of near- constant total emissions.

• Future methane emissions from wetlands are likely to increase in a warmer and wetter climate

Nitrogen CompundsNitrogen Compunds

• Observed increases in nitrous oxide and nitric oxide emissions are very likely linked to the ‘acceleration’ of the nitrogen cycle driven by human activity, including fertilizer use, intensification of agricultural activity and fossil fuel combustion

Changes in the indices of the global agricultural N cycle

Changes in the emissions of fuel combustion NOx and atmospheric N2O mixing ratios

Tropospheric NOTropospheric NO22

• Tropospheric column of nitrogen dioxide from (a) satellite measurements (GOME) and (b) an ensemble of 17 global chemical transport models for the year 2000.

Atmospheric chemistry modelsSatellite measurements

Tropospheric OzoneTropospheric Ozone

• New model estimates suggest that– The input of ozone (500 Tg/yr) is smaller than previously estimated

(700 Tg/yr)– The photochemical production (5000 Tg/yr) and destruction (4500

Tg/yr) are larger than previously estimated (3400 and 3500 Tg/yr)

• This implies greater sensitivity of ozone to changes in tropospheric chemistry and emissions.

Stratospheric Ozone RecoveryStratospheric Ozone Recovery

• The recovery of stratospheric ozone will be influenced by stratospheric cooling and by changes in the atmospheric circulation resulting from enhanced CO2.

• Colder temperatures will favor polar ozone destruction by chlorine activated on polar stratospheric clouds.

Air Quality and Climate ChangeAir Quality and Climate Change

• Future climate change may cause significant air quality degradation by changing

– The dispersion rate of pollutants

– The chemical environment for ozone and aerosol generation

– The strength of emissions from the biosphere, fires and dust

• The sign and magnitude of these effects are highly uncertain and will vary regionally.

Ozone Pollution and Climate ChangeOzone Pollution and Climate Change

• Future climate change may cause either an increase or a decrease in background tropospheric ozone, due to the competing effects of water vapor and higher stratospheric input

• Regional ozone pollution is expected to increase due to higher temperatures and weaker circulation

The daily maximum eight-hour average ozone concentration

ContentsContents





5. Reactive Gases

6. Aerosol

Aerosol Particles and ClimateAerosol Particles and Climate

Center of Ocean-Land-Atmosphere studies

SulfateSulfate

Fossil fuel burning (72%), biomass burning (2%),

natural dimethylsulphide (DMS) emissions by

marine phytoplankton (19%), volcanoes (7%).

Fossil fuel burning (72%), biomass burning (2%),

natural dimethylsulphide (DMS) emissions by

marine phytoplankton (19%), volcanoes (7%).

Fossil fuel and biofuel burning and natural biogenic emissions

Fossil fuel and biofuel burning and natural biogenic emissions

Incomplete combustion processes (fossil fuel and

biomass burning)

Incomplete combustion processes (fossil fuel and

biomass burning)

Industrial practicesIndustrial practices

Organic Carbon Aerosol

Organic Carbon Aerosol

Black CarbonBlack Carbon

Nitrate AerosolNitrate Aerosol

Direct Effect: Scattering

dominates than absorbing

Indirect effect as CCN

: Cloud albedo effect

Indirect effect as CCN

: Cloud lifetime effect

Indirect effect : Evaporation of cloud

particles through absorption of solar radiation by soot

Cooling

Warming

Biomass burningBiomass burning Biomass Burning Aerosol

Biomass Burning Aerosol

Agricultural practices, changes in surface water and industrial practices

Agricultural practices, changes in surface water and industrial practices

Mineral Dust Aerosol

Mineral Dust Aerosol

Aerosols (i.e., dust) also deliver nitrogen (N), phosphorus (P) and iron (Fe) to the Earth’s surface these nutrients could increase uptake of CO2 by marine and terrestrial ecosystems.

Aerosol and ClimateAerosol and Climate

• Sulfate aerosol particles are responsible for the globally- averaged temperature increase being lower than expected from greenhouse gas concentrations alone.

• Aerosols affect the radiative fluxes by scattering and absorbing solar radiation

• Panels a and b show effect in 2071-2100 of removing all anthropogenic aerosols in 2000. Panel c shows temperature evolution with aerosol burden (blue) and without aerosol burden (red) relative to 1961-1990 mean. [Brasseur and Roeckner 2005]


• Aerosols interact with clouds and the hydrological cycle by acting as cloud condensation nuclei (CCN) and ice nuclei.

• A larger increase in CCN increases cloud albedo and reduces precipitation efficiency, which result in a reduction of the global annual mean net radiation at the top of the atmosphere.

•These effects may be partly offset by evaporation of cloud droplets due to absorbing aerosols and/or by more ice nuclei.


• Sulphate aerosol particles are responsible for globally averaged temperatures being lower than expected from greenhouse gas concentrations alone.

• Aerosols affect radiative fluxes by scattering and absorbing solar radiation (direct effect, see Chapter 2). They also interact with clouds and the hydrological cycle by acting as cloud condensation nuclei (CCN) and ice nuclei. For a given cloud liquid water content, a larger number of CCN increases cloud albedo (indirect cloud albedo effect) and reduces the precipitation efficiency (indirect cloud lifetime effect), both of which are likely to result in a reduction of the global, annual mean net radiation at the top of the atmosphere. However, these effects may be partly offset by evaporation of cloud droplets due to absorbing aerosols (semi-direct effect) and/or by more ice nuclei (glaciation effect).

• The estimated total aerosol effect is lower than in TAR mainly due to improvements in cloud parametrizations, but large uncertainties remain.


• Response in the net radiation at the top of the atmosphere from pre-industrial times to present-day due to the global mean total anthropogenic aerosol effects


• Global mean change in precipitation from pre-industrial times to present-day due to the global mean total anthropogenic aerosol effects


• Global mean change in net solar radiation at the surface due to total anthropogenic aerosol effects (direct and non direct effects)


• The radiative forcing resulting from the indirect cloud albedo effect was estimated in Chapter 2 as –0.7 W m–2 with a 90% confidence range of –0.3 to –1.8 W m–2. Feedbacks due to the cloud lifetime effect, semi-directeffect or aerosol-ice cloud effects can either enhance or reduce the cloud albedo effect.

• Climate models estimate the sum of all aerosol effects (total indirect plus direct) to be –1.2 W m–2 with a range from –0.2 to –2.3 W m–2 in the change in top-of-the-atmosphere net radiation since preindustrial times.

• The magnitude of the total aerosol effect on precipitation is more uncertain, with model results ranging from almost no change to a decrease of 0.13 mm day–1.

Dust EmissionsDust Emissions

• Climate change is likely to affect dust sources

• Deposition of dust particles containing limiting nutrients can enhance photosynthetic carbon fixation on land and in the oceans.

Physical Science Basis of Climate Change: IPCC 2007 Emilia K. Jin Chapter 7: Couplings Between...

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