Atmosphere and Climate Change

Climate  Weather is the conditions that occur in the atmosphere are over a short period of time.  Climate is how the atmosphere "behaves" over relatively long periods of time.  When we talk about climate change, we talk about changes in long-term averages of daily weather.

Past Climate Change  The Earth's climate has changed throughout history.  From glacial periods (or "ice ages") where ice covered significant portions of the Earth to interglacial periods where ice retreated to the poles or melted entirely - the climate has continuously changed.

Past Climate Change  Scientists have been able to piece together a picture of the Earth's climate dating back decades to millions of years ago by analyzing a number of substitute, or "proxy," measures of climate.

Past Climate Change  Examples of “proxy” measures include: –ice cores –boreholes –tree rings –glacier lengths –pollen remains –ocean sediments –studying changes in the Earth's orbit around the sun.

Past Climate Change  Causes of Change Prior to the Industrial Era (pre-1780) –Changes in the Earth's orbit –Changes in the sun's intensity –Volcanic eruptions –Changes in ocean currents

Past Climate Change  The Last 2,000 Years –During the last 2,000 years, the climate has been relatively stable. –Scientists have identified three departures from this stability, known as the Medieval Warm Period, the Little Ice Age and the Industrial Era

Past Climate Change  Prior to the Industrial Era, the Medieval Warm Period and Little Ice Age had defined the upper and lower boundaries of the climate's recent natural variability and are a reflection of changes in climate drivers (the sun's variability and volcanic activity) and the climate's internal variability (referring to random changes in the circulation of the atmosphere and oceans).

Recent Climate Change  Since the Industrial Revolution (around 1750), human activities have substantially added to the amount of heat-trapping greenhouse gases in the atmosphere.  The burning of fossil fuels and biomass (living matter such as vegetation) has also resulted in emissions of aerosols that absorb and emit heat, and reflect light.

Factors That Determine Climate   Elevation or Altitude   Prevailing global wind patterns   Latitude and angles of the suns rays   Topography   Distance from the equator   Ocean circulation patterns   Volcanic activity

The Ozone Layer  "The ozone layer" refers to the ozone within stratosphere, where over 90% of the earth's ozone resides.

The Ozone Layer  The ozone layer absorbs a portion of the radiation from the sun, preventing it from reaching the planet's surface.  Most importantly, it absorbs the portion of ultraviolet light called UVB.  UVB has been linked to many harmful effects, including various types of skin cancer, cataracts, and harm to some crops, certain materials, and some forms of marine life.

The Ozone Layer  The ozone layer absorbs 97-99% of the sun's high frequency ultraviolet light, light which is potentially damaging to life on earth.  Every 1% decrease in the earths ozone shield is projected to increases the amount of UV light exposure to the lower atmosphere by 2%.

Chemicals That Cause Ozone Depletion  Chlorofluorocarbons (CFCs) –used as refrigerants, solvents, foam blowing agents, fire extinguishing agents – CFCs have atmospheric lifetimes long enough to allow them to be transported by winds into the stratosphere. –Because they release chlorine or bromine when they break down, they damage the protective ozone layer.

The Ozone Hole  CFCs, HCFCs, carbon tetrachloride, methyl chloroform, and other gases release chlorine atoms, and halons and methyl bromide release bromine atoms  It is these atoms that actually destroy ozone.  It is estimated that one chlorine atom can destroy over 100,000 ozone molecules before it is removed from the stratosphere.

Protecting the Ozone Layer  Montreal Protocol on Substances That Deplete the Ozone Layer –International treaty designed to protect the ozone layer by phasing out the production of a number of substances believed to be responsible for ozone depletion. –Since the Montreal Protocol came into effect, the atmospheric concentrations of the most important chlorofluorocarbons and related chlorinated hydrocarbons have either leveled off or decreased

Global Warming  Global warming is the increase in the average temperature of Earth's near- surface air and oceans since the mid- 20th century and its projected continuation.

The Greenhouse Effect  Energy from the Sun drives the Earth's weather and climate.  The Earth absorbs energy from the Sun, and also radiates energy back into space.  However, much of this energy going back to space is absorbed by “greenhouse” gases in the atmosphere

The Greenhouse Effect  Because the atmosphere then radiates most of this energy back to the Earth’s surface, our planet is warmer than it would be if the atmosphere did not contain these gases.  Without this natural "greenhouse effect," temperatures would be about 60ºF lower than they are now, and life as we know it today would not be possible.

Greenhouse Gases  Carbon dioxide  Water vapor  Methane  Nitrous oxide  Fluorinated gases –Hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride

Carbon Dioxide  Carbon dioxide enters the atmosphere through the burning of fossil fuels (oil, natural gas, and coal), solid waste, trees and wood products, and also as a result of other chemical reactions (e.g., manufacture of cement).  Carbon dioxide is also removed from the atmosphere (or “sequestered”) when it is absorbed by plants as part of the biological carbon cycle.

Carbon Dioxide (non-energy related) Emissions  Cement manufacture –calcium carbonate is heated to produce lime –In 1998, the United States manufactured an estimated 85.5 million metric tons of cement, resulting in the direct release of carbon dioxide containing about 10.6 million metric tons of carbon into the atmosphere.

Measuring Carbon Dioxide  The rise of carbon dioxide gas in our atmosphere has been measured continuously since 1958.

Methane Emissions  Sources include energy production and consumption such as: –coal mining –natural gas systems  Waste management –landfill gas  Agriculture –manure management –cattle (enteric fermentation) –rice cultivation

Nitrous Oxide (N2O) Emissions  Agricultural soil management –nitrogen fertilization  Mobile sources  Acidic acid production –used to make nylon

Expected Consequences of GHG Concentration Increases  Temperature: Global temperatures are rising.  Observations collected over the last century suggest that the average land surface temperature has risen °C ( °F) in the last century.

Expected Consequences of GHG Concentration Increases  Rising Sea Level –Hotter temperatures mean ice -- glaciers, sea ice and polar ice sheets -- is melting, increasing the amount of water in the world's seas and oceans.

Expected Consequences of GHG Concentration Increases  Shrinking Glaciers –In the span of a century, glaciers in Montana's Glacier National Park have deteriorated from 150 to just 35. –And the Himalayan glaciers that feed the Ganges River, which supplies drinking and irrigation water to 500 million people, are reportedly shrinking by 40 yards (37 meters) each year.

Montana's Glacier National Park

Expected Consequences of GHG Concentration Increases  Heat Waves –Extreme heat waves are happening two to four times more often now, steadily rising over the last 50 to 100 years, and are projected to be 100 times more likely over the next 40 years.

Expected Consequences of GHG Concentration Increases  Storms and Floods –Warm waters give hurricanes their strength, and scientists are correlating the increase in ocean and atmospheric temperatures to the rate of violent storms.

Expected Consequences of GHG Concentration Increases  Drought –As the climate warms, experts estimate drought conditions may increase by at least 66 percent [source: Scientific American]. Scientific AmericanScientific American –An increase in drought conditions leads quickly to a shrinking water supply and a decrease in quality agricultural conditions.

Expected Consequences of GHG Concentration Increases  Disease –Warmer temperatures along with associated floods and droughts are encouraging worldwide health threats by creating an environment where mosquitoes, ticks, mice and other disease- carrying creatures thrive.

Expected Consequences of GHG Concentration Increases  Economic Consequences –Consumers face rising food and energy costs along with increased insurance premiums for health and home. –Governments suffer the consequences of diminished tourism and industrial profits, soaring energy, food and water demands, disaster cleanup and border tensions.

Expected Consequences of GHG Concentration Increases  Loss of Biodiversity –As many as 30 percent of plant and animal species alive today risk extinction by 2050 if average temperatures rise more than 2 to 11.5 degrees F (1.1 to 6.4 degrees C) [sources: EPA, Scientific American]. –Such extinctions will be due to loss of habitat through desertification, deforestation and ocean warming, as well as the inability to adapt to climate warming.

Expected Consequences of GHG Concentration Increases  Destruction of Ecosystems –Changing climatic conditions and dramatic increases in carbon dioxide will put our ecosystems to the test, threatening supplies of fresh water, clean air, fuel and energy resources, food, medicine and other matters we depend upon not just for our lifestyles but for our survival.

Coral Bleaching