Weather • Solar radiation
Weather • Flowing air and convection currents • West to east • Jet streams, Earth’s rotations and air pressure gradients • Polar jet stream • Fronts • Regions of rapid weather change
Climate • Average temperature and precipitation expected throughout a typical year in a given region • Major changes in climate are a major threat to the structure and function of ecosystems
Climates in the past • Annual mean global surface atmospheric temperature • Periods of cooling and warming • General increase in temperature
Climates in the past • Proxies • Tree rings • Pollen deposits • Changes in landscapes • Marine sediments • Corals • Ice cores • Thickness • Gas content (CO2, CH4) • Isotopes • Milankovitch cycles • Rapid changes • Younger Dryas
Oceans and Atmosphere • Oceans have an innate heat capacity • Thermohaline circulation • Conveyor system • Affect the density of seawater • One cycle is competed in 1000 years • Heinrich events • Fresh water in the oceans can change climate
Global climate change • Factors that influence the climate include: • Internal components • Oceans, the atmosphere, snow cover, sea ice • External factors • Solar radiation, Earth’s rotation, slow changes in our planet’s orbit, and the gaseous makeup of our atmosphere
Radiative forcing: the influence a particular factor has on the energy balance of the atmosphere – ocean – land system. • Factors can either be positive (warming) or negative (cooling)
Warming processes • Infrared radiation and the greenhouse effect
Warming processes • Greenhouse gases (GHGs) • Water vapor • Carbon dioxide • Methane • Nitrous oxides • Ozone • CFCs
Cooling processes • The planetary albedo • Clouds • Snow and ice • Volcanoes • Sulphate aerosols • Ozone depletion • Solar variability (11 year cycle)
So… • Global atmospheric temperatures are a balance between positive and negative forcing from natural causes (volcanoes, clouds, natural GHGs, solar radiation) and anthropogenic causes (sulfate aerosols, soot, ozone depletion, increases in GHGs)
The greenhouse gases • Carbon dioxide • Svante Arrhenius: “differences in CO2 levels in the atmosphere could greatly affect Earth’s energy budget”; he believed this change would be beneficial. • Charles Keeling, 1958, first measures of CO2 levels in Hawaii.
The greenhouse gases Sources of CO2 emissions from fossil fuel burning • Carbon dioxide • Sources: • Fossil fuels • Burning of forest trees • Industrial processes • Sinks • Oceans • Terrestrial ecosystems
Global carbon cycle Atmosphere – ocean exchange 92 (+/-0,6) Atmospheric CO2 750 6,6 Combustion 90 Oceanic dissolved inorganic carbon Surface – 1020 Depths - 38100 Fossil fuel carbon 4130 62,4 (+/-0,8) Photosynthesis 61 Respiration Terrestrial biosphere Living – 600 – 1000 Dead - 1200
The greenhouse gases • Water vapor • Absorbs infrared energy • Most abundant GHG • Increases the sensitivity of climate to increased anthropogenic GHG
The greenhouse gases • Methane • Sources • Microbial fermentation (wetlands, landfills, cattle, manure) • Coal and oil deposits • Natural gas pipelines
The greenhouse gases • Nitrous oxide • Sources • Agriculture • Burning of biomass • Fossil fuels • It has a long resistance time (114 years) • Also contributes to the destruction of stratospheric ozone
The greenhouse gases • Ozone • Short lived • Source • Reactions of sunlight with pollutants from automobiles, burning forests and agricultural wastes
The greenhouse gases • CFCs and other halocarbons • Long lived (50 – 100 years) • Used as refrigerants, solvents and fire retardants • Montreal Accord (1987) prohibited the use of CFCs
Evidence of Climate Change • 1988, the UN Environmental Program and the World Meteorologial Society established the Intergovernmental Panel on Climate Change (IPCC) • 3 working groups were established • Working group I: to asses scientific issues • Working group II: to evaluate the impact on global climate change and prospects for adapting to it • Working group III: to investigate ways of mitiating the effects
Evidence of Climate Change • The work of the IPCC has been guided on two basic questions: • Risk assessment: is the climate system changing, and what is the impact on society and ecosystems? • Risk management: how can we manage the systems through adaptation and mitigation?
Working group I third assessment (2001) • An increasing body of observations gives a collective picture of a warming world and other changes in climate system • Correlation CO2 / global atmospheric temperatures • Heat content in oceans increased dramatically • Retreat of glaciers • Thinning of polar ice • Global temperature has increased 1oF • Increase in precipitation, greater frequency of El Niñoevents • More frequent and intense droughts, heat waves, rainfall and tornadoes • Rise in sea level between 0,1 and 0,2 mts (2mm/year)
Working group I third assessment (2001) • Emissions of GHGs and aerosols due to human activities continue to alter the atmosphere in ways that are expected to affect the climate. • GHGs and aerosols continue to increase in the atmosphere
Working group I third assessment (2001) • Confidence in the ability of models to project future climate has increased • Forecasts are more accurate • Coupled general circulation models (CGCM) are capable of simulating long-term climatic conditions • The main purpose of the models is to project the future global climate.
Working group I third assessment (2001) • There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities
Working group I third assessment (2001) • Human influences will continue to change atmospheric composition throughout the 21st century • Different scenarios project a rise in CO2 levels as a consequence of burning fossil fuels • The scenarios demonstrate the crucial importance of our energy choices.
Working group I third assessment (2001) • Global average temperature and sea level are projected to rise under all IPCC scenarios • The global averaged surface temperature is projected to increase by 1.4 to 5.8oC over the period 1990 to 2100. • Climate will be seriously affected • Sea level is projected to increase from 9 to 88cm
Working group I third assessment (2001) • Anthropogenic climate change will persist for many centuries • Once atmospheric greenhouse gas levels are stabilized, temperatures and sea levels will continue to rise for hundreds of years because of the slow response time of the oceans.
Working group I third assessment (2001) • Further action is required to address remaining gaps in information and understanding • More research is needed on current climate variables such as: • Occurrence and impacts of clouds • Changes in glaciers and sea ice • Functioning of the carbon cycle • Natural variability of climate • Impacts of aerosols
Response to climate change • Mitigation: take action to reduce emissions • Adaptation: anticipate some harm and plan adaptive responses
Why should we take action? • Precautionary principle: “the lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation” • Polluter pays principle: polluters should pay for the damage their pollution causes • Equity principle: the rich and privileged should care about those generations which follow
Mitigation: taking steps towards sustainability • What has been done? • Framework convention on climate change (FCCC) • Goal to stabilize greenhouse gas levels in the atmosphere, starting by reducing greenhouse gas emissions to 1990 levels by the year 2000 • Kyoto protocol • Goal to reduce emissions of six GHGs to 5,2% below 1990 levels to be achieved by 2012
Mitigation • What has been done? • U.S Policy • Opposed to the Kyoto protocol • Compromised to protect the environment by reducing CO2 emissions and other GHGs • Global climate change initiative • 18% cut in emissions intensity over the next 10 years • U.S climate change science program (CCSP) • Seeks to address several issues on climate science • States and corporations • Fourteen states are adopting renewable portfolio standards to regulate CO2 emissions
Adaptation • Climate change is already happening? • Crop yields are likely to be reduced in tropical and subtropical regions as warming and droughts become more severe • Water is more scarce in many regions • Increased heat and moisture will lead to an increase in infectious disease • Increased intensity and frequency of storm events
Adaptation • What is being done? • New funds • Least Developed Countries Fund: to advice countries on adaptation strategies • Special Climate Change Fund: to provide additional financial assistance to developing countries affected by climate change
Adaptation • Specific adaptation strategies: • Improved governance • Vulnerability assessments • Access to accurate information on climate change • Integration of impacts into economic processes.
Radiation and importance of the shield • Shorter wavelengths are more energetic and therefore can cause more damage
Formation and breakdown of the shield O2 + UVB O + O O + O2 O3 O + O3 O2 + O2 O3 + UVB O + O2
Halogens in the atmosphere CFCl3 + UV Cl + CFCl2 Cl + O3 ClO + O2 Chlorine catalytic cycle ClO + ClO 2Cl + O2