Physical Science Basis of Climate Change : IPCC 2007

Center of Ocean-Land-Atmosphere studies CLIM759: Topics in Climate Dynamics GEOG 670: Applied Climatology Physical Science Basis of Climate Change: IPCC 2007 Chapter 7: Couplings Between Changes in theClimate System and Biogeochemistry Emilia K. Jin Thanks to Dr. C. Sabine and Prof. E. Sarachik, Mar 4, 2008

Contents Center of Ocean-Land-Atmosphere studies • Importance of Feedbacks • Global Carbon -Climate System • Land - Climate Interaction • Ocean - Climate Interaction • Reactive Gases • 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…

Contents Center of Ocean-Land-Atmosphere studies • Importance of Feedbacks • Global Carbon -Climate System • Land - Climate Interaction • Ocean - Climate Interaction • Reactive Gases • Aerosol

Couplings Between Changes in theClimate System and Biogeochemistry Center of Ocean-Land-Atmosphere studies • 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 betweenthe physical climate system and the land surface, the carbon cycle,chemically reactive atmospheric gases and aerosol particles. •  There are large uncertaintiesto provide a simple quantitative description. Biogeochemical cycling • 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 uptakeby the ocean and its ecosystems. Earth’s Climate Nonlinearinteractions between/within thedifferent components of the Earth system Radiativeproperties of the atmosphere Complexconnected physical, chemical and biological processesoccurring in the atmosphere, land and ocean. Composition of the atmosphere Biophysical state of the Earth’s surface : LLGHGs, CO2, CH4, N2O, ozone, and aerosol particles.

Radiative Forcing Components and Their Feedbacks to the Climate System Center of Ocean-Land-Atmosphere studies • 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.

Carbon Dioxide Center of Ocean-Land-Atmosphere studies Raupachet al., 2007 PNAS

Carbon Dioxide Center of Ocean-Land-Atmosphere studies Raupachet al., in press. PNAS

Fraction of the CO2 emitted by human activities which remains in the atmosphere Center of Ocean-Land-Atmosphere studies airborne fraction =atm / (fossil fuel + cement + land use emissions)

Carbon Dioxide Center of Ocean-Land-Atmosphere studies • • 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 CO2 Concentration Remained in the ATM.

Are there changes in the efficiency of the land and/or ocean sinks for CO2 ? Center of Ocean-Land-Atmosphere studies

Center of Ocean-Land-Atmosphere studies IPCC SRES Emission Scenarios(The Emission Scenarios of the IPCC special Report on Emission Scenarios) Pg (Petagram) =1015 g = Gt (Gigaton)

The IPCC Assessments of ClimateChange and Uncertainties Center of Ocean-Land-Atmosphere studies The six IPCC scenarios arespline fits to projections (initialized with observations for 1990) of possiblefuture emissions for four scenario families, A1, A2, B1, and B2, which emphasizeglobalized vs. regionalized development on the A,B axis and economicgrowth vs. environmental stewardship on the 1,2 axis. Three variants of the A1(globalized, economically oriented) scenario lead to different emissions trajectories:A1FI (intensive dependence on fossil fuels), A1T (alternative technologieslargely replace fossil fuels), and A1B (balanced energy supply betweenfossil fuels and alternatives). A1 Scenarios – Fast economic growth and globalization These describe 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.There are increasing levels of international cultural and social interactions and regional differences in income are substantially reduced.There are three types of A1 scenarios that describe different directions of technological change in the energy industry: A1F1 is fossil fuel intensive, A1T puts a greater emphasis on non-fossil energy sources, while societies in A1B use a variety of energy sources. A1B also assumes that technologies to exploit all energy sources will advance at similar rates. A2 Scenarios – Rising population and slower technical innovation These describe a very heterogeneous world. In this scenario, countries and regions seek to achieve self-reliance and to preserve their local identities.The birth rates in different regions become more and more similar, which results in continuously increasing population. Economic development is primarily regionally oriented. Per capita economic growth and technological change are more fragmented and slower than for other scenarios. B1 Scenarios – Service economy and global solutions These have the same global population growth as the A1 scenarios. But its economic structures evolve rapidly towards a service and information economy. Material resources are less exploited and clean and resource-efficient technologies are introduced.The emphasis is on global solutions to economic, social and environmental sustainability, but without additional climate initiatives. B2 Scenarios These describe a world in which the emphasis is on local solutions to economic, social and environmental sustainability. It is a world with continuously growing population (but at a slower rate than the A2 scenarios). The rate of economic development is neither breakneck nor stalling.Technological change is less rapid but more diverse than in the A1 and B1 scenarios. While the scenarios are also oriented towards environmental protection and social equity, they focus on local and regional levels.

Projected Future Warming Center of Ocean-Land-Atmosphere studies Figure 9.13, IPCC TAR

WRE Stabilization Scenarios and Permissible Emissions Center of Ocean-Land-Atmosphere studies WRE: Wigley, Richels, and Edmonds (WRE 1996) used in IPCC TAR Figure 10.22, IPCC AR4

WRE 500 Permissible Emissions and “THE GAP” Center of Ocean-Land-Atmosphere studies

Coupled Climate-Carbon Cycle Models Sequester Center of Ocean-Land-Atmosphere studies 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 Scenarios Center of Ocean-Land-Atmosphere studies Raupachet al., 2007 PNAS

Coupling the Biogeochemical Cycles with the Climate System Center of Ocean-Land-Atmosphere studies • 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 processes • involved and highlights the role of biogeochemical processes in the climate system.

Pre 1990s View of the Global Carbon Cycle Center of Ocean-Land-Atmosphere studies

In the early 1990s the World Ocean Circulation Experiment (WOCE), the Joint Global Ocean Flux Study (JGOFS), and the NOAA/OACES program joined forces to conduct a global survey of CO2 in the oceans. Center of Ocean-Land-Atmosphere studies >70,000 sample locations; DIC ± 2 µmolkg-1; TA ± 4 µmolkg-1 http://cdiac.esd.ornl.gov/oceans/glodap/Glodap_home.htm

Column inventory of anthropogenic CO2that has accumulated in the ocean Center of Ocean-Land-Atmosphere studies

Carbon changes between 1800 and 1994 Center of Ocean-Land-Atmosphere studies 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 1990s Center of Ocean-Land-Atmosphere studies  Largest variability & uncertainties are in carbon fluxes from land use change and 'residual terrestrial carbon sink'.

The Global Carbon Budget [Pg C] Center of Ocean-Land-Atmosphere studies 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 Scenarios Center of Ocean-Land-Atmosphere studies • 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 Climate Center of Ocean-Land-Atmosphere studies • 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 few centuries. 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 Climate Center of Ocean-Land-Atmosphere studies • 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 1980s downwards 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 an additional 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.

Terrestrial Ecosystems and Climate Center of Ocean-Land-Atmosphere studies Carbon cycle Temperature, Precipitation, CO2, Nutrients Climate Biogeophysical biogeochemical processes Vegetation cover, Biomes, Productivity, Respiration of vegetation and soil, Fires Photosynthetic productivity Terrestrial biosphere Balance of fluxes Non-radiative (e.g., watercycle related processes) Radiative (e.g. albedo) High-latitudes: strong snow albedo feedback Semiarid tropical systems: radiative and hydrological feedbacks Details of vegetation

Example: Terrestrial Ecosystems and Climate Center of Ocean-Land-Atmosphere studies Rainfall increase in a semi-arid system Atmosphere: enhancedcarbon uptake Alter the partitioning ofcarbon between the atmosphere and the land surface Photosynthetic productivity increase Ecosystem structure shift: Organic carbon compoundsin soilsare respired. Temp. decrease Net flux of carbon from the atmosphere to the land surface From boreal forest to Tundra Larger biomass of trees than herbs and shrubs Carbon storage increase in ecosystem. Rainfall decrease Net flux of carbon from the land surface to the atmosphere From tropical rainforest to savannah Less biomass of trees Carbon storage decrease in ecosystem.

Feedbacks Between Changes in the Land Surface and Climate Center of Ocean-Land-Atmosphere studies • 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 in the Land Surface and Climate Center of Ocean-Land-Atmosphere studies • 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 System Center of Ocean-Land-Atmosphere studies • 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.

Ocean Ecosystems and Climate Center of Ocean-Land-Atmosphere studies Near-surface density stratification,ocean circulation, temperature, salinity, wind field, sea ice cover Chemical composition of the atmosphere: CO2, N2O, O2, dimethyl sulphide (DMS), sulphate aerosol Near-surface radiation budget Climate Ocean Ecosystem Marine biota: Changesin the marine albedo and absorption of solar radiation (bioopticalheating) Ocean Ecosystem • 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 Climate Center of Ocean-Land-Atmosphere studies Surface Temp. increase Enhanced stratification Reductions in vertical mixing and overturning circulation: Decrease the return of required nutrients to the surface ocean The sign of the cumulative feedback to climate of all these processes is still unclear. Increased photosynthetic fixation of CO2 Alter the vertical export of carbon to the deeper ocean. Dust deposition to the ocean surface The supply of micronutrients, in particular iron Increased photosynthesis Ocean acidification due to uptake of anthropogenic CO2 Alter the biological production Export from the surface ocean of organic carbon and calcium carbonate (CaCO3) Shifts in ocean ecosystem structure and dynamics CO2

Sensitivity of ocean carbon uptake to climate change Center of Ocean-Land-Atmosphere studies • Mechanisms : • -Increasing Sea Surface Temperature (SST) decreases CO2 solubility. • - Decreased Mixing prevents • the penetration of C ant. • Decrease in Biological Production reduces the amount of carbontransported to depth. • …..

Sensitivity of ocean carbon uptake to climate change Center of Ocean-Land-Atmosphere studies No clear global relationship :  Need to break down the responses at regional levels.  Need to consider natural / anthropogenic carbon separately…..

Center of Ocean-Land-Atmosphere studies What we know about the biological impacts of ocean acidification 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) Courtesy of Dr. R. Feely

Atmospheric Chemistry and Climate Center of Ocean-Land-Atmosphere studies Atmospheric oxidants (e.g. O3) Polluted area Concentration increase Radiative warming Tropospheric chemical O3precursors(carbon monoxide, CH4, non-methane hydrocarbons, nitrogenoxides) Fossil fuel, Biomass burning,Agriculturalpractices Concentration increase Slight warming Stratospheric Ozone Manufactured halocarbons Concentration decrease Slight cooling Slow down 1980s-1990s Late 1990s CH4 Source strength Concentration increase Slight warming Nitrous oxide Agricultural activities Concentration increase Slight warming

Atmospheric Chemistry and Climate Center of Ocean-Land-Atmosphere studies • Changes in atmospheric chemical composition due to climate changes Changes in atmospheric chemical composition thatcould result from climate changes Increased watervapour Photochemical production of the hydroxyl radical (OH) Destroys many atmospheric compounds Other chemistry-relatedprocesses: The importance of theseeffects is not yet well quantified. Frequency oflightning flashes in thunderstorms Produce nitrogenoxides Scavenging mechanisms Remove soluble speciesfrom the atmosphere Intensity and frequency of convectivetransport events Natural emissions of chemical compounds(e.g., biogenic hydrocarbons by the vegetation, nitrous andnitric oxide by soils, DMS from the ocean) Surfacedeposition on molecules on the vegetation and soils More frequent occurrenceof stagnant air events in urban or industrial areas Enhancethe intensity of air pollution events

Biogeochemistry, Atmospheric Chemistry and Climate Change Center of Ocean-Land-Atmosphere studies • : 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 Compounds in the Atmosphere Center of Ocean-Land-Atmosphere studies

Physical Science Basis of Climate Change : IPCC 2007