publiclectures3

Slide1: 

GLOBAL CLIMATE CHANGE: WHY THE SKEPTICS ARE WRONG JUNE 27, 2006 John Harte University of California, Berkeley

Slide2: 

The increase in atmospheric carbon dioxide is primarily due to world energy consumption and secondarily due to deforestation.

Slide3: 

Sunlight Heat Greenhouse gases Heat The greenhouse gases trap outgoing heat and radiate it back to the surface

Slide4: 

What is the effect on global average surface temperature of doubling the atmospheric concentration of carbon dioxide? The direct effect of heat absorption by the CO2: + 1.2 oC The indirect (feedback) effects: + 0.3 to 3.4 oC melting ice and snow increases absorption of sunlight (ice-albedo effect) warmer air holds more water vapor, another greenhouse gas warmer air results in different cloud characteristics TOTAL: + 1.5 to 4.6oC The central prediction of current climate models:

Slide5: 

Temperatures During the Past Ice Age oF oC Thousands of years ago Should we worry about +4 oC change? 6oC

Climate Models Have Good Predictive Power….: 

Climate Models Have Good Predictive Power…. 0.7oC increase in past Century; Up to 5oC this century

Fingerprint of Global Warming: 

Fingerprint of Global Warming Stratosphere cools as surface warms Temperature rises faster at night than day Temperature rises faster in winter than summer High latitudes warm more than low latitudes If global warming were caused by a brightening sun, then the stratosphere would warm and temperature rise would be greatest in daytime Models predict, and the data show that:

Slide8: 

We are entering uncharted territory in human experience. If nothing is done to slow greenhouse gas emissions. . . CO2 concentrations will be more than 700 ppm by 2100 Temperatures may be warmer than any time since the dinosaurs! 2100 Source: OSTP today

Slide9: 

IMPACTS OF GLOBAL WARMING *** Greater intensity, frequency & duration of harmful summer heat waves *** Sea level rise of at least ½ m by 2100; loss of some island nations *** Melting of glaciers and sea ice; loss of alpine and arctic habitat; polar bears! *** Reduced snow pack; loss of irrigation water for crops *** Coral reef degradation due to bleaching *** Near unanimity among scientists active in the field; high level of confidence in predictions

Slide10: 

** Increased intensity and possibly frequency of hurricanes and droughts ** Reduced crop yields because of extreme events and persistent drought ** Increased threat of major wildfires MORE IMPACTS OF GLOBAL WARMING ** Consensus exists on the underlying science and facts; work needed to sharpen predictions

Slide11: 

* Sea level rise up to 40 feet because of Greenland and Antarctica ice melt (“bi-polar disorder”); catastrophic damage to huge numbers of people and to much coastal infrastructure * Extinction episode comparable to K-T boundary; catastrophic loss of ecosystem services * Major spread of infectious tropical and subtropical diseases to the mid-latitudes * Agreement that the problem is real and of serious importance; data gaps and some basic science still to be resolved AND STILL MORE IMPACTS

Slide12: 

Pre-historical climate change far exceeds the anticipated changes in the next 100 years, so no need to worry. Variation in sunlight probably explain the recent warming trend Satellite data contradict the evidence for a warming trend. A cooling trend during 1940-1970 contradicts the global warming concept The world should welcome global warming because it will help moderate the impacts of the impending ice age. Global warming will be good for agriculture; CO2 enrichment Global warming theory has never been proven! Reducing emissions will severely damage our economy Prevailing Myths about Global Warming

Slide13: 

Future energy policy will determine this This warming has already occurred 1000 2100 Year Global average surface temperature is heading not only far outside the range of variation of the last 1000 years but outside the range experienced in the tenure of Homo sapiens on Earth.

Slide14: 

2000 2050 14 Climate Stabilization 7 Gigatons Carbon Emitted per Year 1950 Doubled emissions from “business as usual” Current emissions The Stabilization Wedges 0 The Climate Challenge Emissions Stabilization

Slide15: 

There are more than 7 wedges to choose from: Here are 15 candidates.

The policy issue in brief : 

The policy issue in brief Society has three options: Prevention, which means measures to reduce the pace & magnitude of the changes in global climate being caused by human activities. Examples of prevention include reducing emissions of GHG, enhancing “sinks” for these gases, and “geoengineering” to counteract the warming effects of GHG. Adaptation, which means measures to reduce the adverse impacts on human well-being resulting from the changes in climate that do occur. Examples of adaptation include changing agricultural practices, strengthening defenses against climate-related disease, and building more dams and dikes. But it’s a moving target! Suffering the adverse impacts that are not avoided by either mitigation or adaptation.

Approaches to prevention: 

Approaches to prevention Improve energy use efficiency (e.g. hybrids) Alter life styles to use less energy (e.g. walk to work) Use cleaner fossil fuels (e.g., gas not coal) Solar energy (wind, photovoltaics, biomass) Sequester carbon from fossil fuels underground Nuclear energy

Approaches to prevention (continued): 

Approaches to prevention (continued) TYPES OF POLICY MEASURES FOR PREVENTION regulations (such as emission standards) and incentives (such as taxes or tax relief) to promote cleaner energy government funding for R&D to insure that technical options are available in the marketplace; incentives for private investment in research, development, & demonstration. IN ADDITION, THE IMPORTANCE OF CONSUMER PRESSURE SHOULD NOT BE UNDERESTIMATED

The renewable option: Is it real?: 

The renewable option: Is it real? SUNLIGHT: ½ % of the world’s land area receives enough sunlight, converted to useable energy at 20% efficiency, to meet the world’s rate of energy use in 2005. WIND: Wind power estimated to be harvestable from windy sites covering 2% of Earth’s land surface is about twice world electricity generation in 2005. BIOMASS: Energy crops grown at the average terrestrial photosynthetic yield on 10% of land area (equal to what’s now used for agriculture) and converted to liquid biofuels at 50% efficiency would provide a little over half of world oil use in 2005. Renewable energy potential is immense, but big concerns about biomass: habitat loss To replace US gasoline, need to grow corn-for-ethanol on the entire combined area of Nebraska, Kansas, Oklahoma, Arkansas, Missouri, Iowa! photovoltaics gives a 20x advantage wrt land use, and don’t need prime land competition between ethanol production and food production resources: water, fertilizer, herbicides, pesticides for biomass, $$$ unanticipated climate effects: Non-CO2 greenhouse gases from biomass production; albedo of land surface

Slide20: 

SUMMARY (1) The consensus view: 1. There is a scientific consensus that human-caused global warming is a serious problem: a. its effects are already observed, b. if preventive steps are not taken, its future consequences for human well being will be large and detrimental 2. Many attractive options exist for reducing carbon dioxide emissions; first and foremost is improving efficiency of energy use.

Slide21: 

SUMMARY (2) A personal view: Global warming is an opportunity as well as a problem; it provides us with a wonderful excuse to: a. Restore to world leadership our dying automobile industry Reduce our dependence on foreign oil and the costs of maintaining that dependence Reduce levels of smog and other air pollutants that result from fossil fuel burning and that impair our health Save industry and consumers billions of $ by becoming more efficient in the use of energy Solving global warming will make us richer, healthier, and more peaceful…what a deal!

The Vostok core data imply additional feedback: 

The Vostok core data imply additional feedback Milankovitch mechanisms are the forcing, and thus the time keeper, but their magnitude is too weak to explain the magnitude of the huge climate variability CO2 release during slight warming must cause more warming! And CO2 uptake during slight cooling must cause more cooling. This feedback is not incorporated in our current GCM’s and suggests that future warming may be worse than we think

How much prevention is needed? (continued): 

How much prevention is needed? (continued) Until a few years ago, many analysts and groups were suggesting a target of about 3°C. This was a compromise: perhaps the highest value that might be tolerable (taking into account potential for adaptation) and at the same time the lowest value that might be achievable (taking into account the known mitigation options and their costs). Recent insights about impacts have led many analysts & groups, over the past few years, to argue for a tighter target, around 2°C. This would mean confining the sum of human influences to the equivalent of CO2’s reaching 400-450 ppmv. Some analysts doubt that so low a target can be achieved.

How much prevention is needed? : 

How much prevention is needed? The conclusion of most analysts is that we are going to need as much prevention as we can get, as quickly as we can get it.

Slide26: 

GLOBAL CLIMATE CHANGE: WHY THE SKEPTICS ARE WRONG JUNE 27, 2006 John Harte University of California, Berkeley