Chapter 19 Global Change

Polar Bears Key link in the polar ecosystem. Indigenous people eat them and use their fur. Arctic fox feed on the leftovers of the seals they leave behind after feeding on the blubber. Warmer air and ocean water causing the polar caps to melt. 1979-2000 average ice present decreased 25-39% from 2006-2009. 2x the size of Texas. Rest of the ice is considerably thinner. Ice melts 3 weeks earlier than 30 years ago. Polar bears weigh 150 pounds less than 30 years ago. Drowning after swimming more than 60 miles to find ice. Pollution and hunter contributors, but not as much as global warming.

Global Change Global change- any chemical, biological or physical property change of the planet. Rates of change have been higher than those that have occurred historically. Global climate change- changes in the climate of the Earth. Some are natural (like El Nino), some anthropogenic (like fossil fuel combustion and deforestation) Global warming- one aspect of climate change, the warming of the oceans, land masses and atmosphere of the Earth.

Section 2

The Greenhouse Effect When radiation from the sun hits the atmosphere, 1/3 is reflected back. Some of the UV radiation is absorbed by the ozone layer and strikes the Earth where it is converted into low-energy infrared radiation. The infrared radiation then goes back toward the atmosphere where it is absorbed by greenhouse gasses that radiate most of it back to the Earth.

Green House Gases Trap heat in the atmosphere like windows trap heat in a car.

Gases in the Atmosphere Two most common: O2 (21%) and N2 (78%)= 99% Neither are greenhouse gases. Neither absorb Infrared Radiation. Only 1% of the gases in the atmosphere are GHG. Natural GHG include: Water vapor: Most common Carbon dioxide: CO2 Methane: CH4 Nitrous oxide: N2O Ozone: O3 Anthropogenic GHG: CFC’s

Greenhouse Warming Potential Estimates how much a molecule of any compound can contribute to global warming over a period of 100 years relative to a molecule of CO2

Interpreting the table Water <1 Doesn’t trap heat as well as CO2 Other gases >1 based upon their ability to absorb more Infrared Radiation or their ability to persist in the atmosphere for a long period of time. Trap heat better then CO2

Section 3

Natural sources of green house gases Volcanic eruptions, decomposition, digestion, denitrification, evaporation, and evapotranspiration

Natural Greenhouse Gases Volcanic eruptions- mainly carbon dioxide Methane – from decomposition Wetlands are the largest natural source. Plants and animals decompose with a lack of oxygen, producing methane. Nitrous oxide- from denitrification Part of the nitrogen cycle (go back and review the nitrogen cycle). Water vapor- from transpiration and evapotranspiration. Varies by region because of varying climates.

Anthropogenic Causes of Greenhouse Gases Most significant sources: Burning of fossil fuels (CO2) Agricultural practices (variety of green house gases) Deforestation (mainly CO2) Landfills (methane) Industrial production- (CFC’s are an example)

Ranking Anthropogenic GHG in U.S.

Increasing CO2 Concentrations David Keeling began measuring CO 2 in 1958. Measured several times per year and found that Carbon dioxide varies seasonable and increased from year to year. Where are our Carbon Sinks? Oceans and Vegetation.

Emissions from the Developed and Developing World Developed World: 20% of the population produces 75% of the CO2

Global Temperatures since 1880 Since 1880 temperatures have increased 0.8°C.

Temperatures and Greenhouse Gas Concentrations in Past 400,000 Years No one was around thousands of years ago to measure temperatures so we use other indirect measurements. Some of these are Changes in species compositions Chemical analyses of ice

Putting It Together We know that an increase in CO2 in the atmosphere causes a greater capacity for warming through the greenhouse effect. When the Earth experiences higher temperatures, the oceans warm and cannot contain as much CO2 gas and, as a result, they release CO2 into the atmosphere.

Section 4

Feedbacks Thawing of permafrost=more decay=more GHG=more heat=more thawing…etc. Which system will predominate? At this point, we don’t know.

Section 5

Consequences to the Environment Because of Global Warming Melting of polar ice caps, Greenland and Antarctica Changing the path of the Thermohaline circulation. Melting of many glaciers around the world Melting of permafrost Rising of sea levels due to the melting of glaciers and ice sheets and as water warms it expands Heat waves Cold spells Change in precipitation patterns Increase in storm intensity Shift in ocean currents

Since 1870 sea levels have risen 9 inches By the end of the 21st century, it is projected to be 7-23 inches greater than 1999 levels.

Consequences to Living Organisms Wild plants and animals can be affected. The growing season for plants has changed and animals have the potential to be harmed if they can’t move to better climates. Humans may have to relocate, some diseases like those carried by mosquitoes could increase and there could be economic consequences. Tourism

The Controversy of Climate Change The fundamental basis of climate change- that greenhouse gas concentrations are increasing and that this will lead to global warming is not in dispute among the vast majority of scientists. What is unclear is how much world temperatures will increase for a given change in greenhouse gases, because that depends on the different feedback loops.

IPCC’s attempt at explaining the “How much” question of Global Warming

Section 6

The Kyoto Protocol In 1997, representatives of the nations of the world went to Kyoto, Japan to discuss how best to control the emissions contributing to global warming. The agreement was that emissions of greenhouse gases from all industrialized countries will be reduced to 5.2% below their 1990 levels by 2012. Developing nations did not have emission limits imposed by the protocol.

Carbon Sequestration An approach involving taking CO2 out of the atmosphere. Some methods include storing carbon in agricultural soils or retiring agricultural land and allowing it to become pasture or forest. Researchers are looking at cost-effective ways of capturing CO2 from the air, from coal-burning power stations, and from other emission sources. This captured CO2 would be compressed and pumped into abandoned oil wells or the deep ocean.