Climate Change - A Basic Overview

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The Basic Overview
Weather describes an area's short term atmospheric conditions, a combination of events such as temperature, wind, humidity, precipitation and pressure that occur over just hours or days. Climate is the bigger picture, a description of a particular area's long term pattern of atmospheric conditions. Climate Change refers to changes in the Earth's overall climate - temperature, precipitation, and storm intensity.

These are the concepts we will cover here very briefly:

The atmosphere and climate
Greenhouse gases and the Greenhouse effect
Expected worldwide impacts from 'climate change'
Potential effects on the USA and Virginia
What can we do about this issue both individually, and as a community?  

The Atmosphere and Climate
The atmosphere is a thin layer of gas wrapped around the Earth, held in place by the forces of gravity. If you were to imagine the Earth shrunk to the size of an apple - the atmosphere would only be the thickness of the skin. This atmospheric skin consists of four layers, each with different temperatures and other properties, although none of the boundaries are visible to the human eye.

The very lowest layer of the atmosphere nearest to the Earth is about 7 miles deep and known as the troposphere. It is in this zone that all weather occurs. Three main factors influence the long term climate of the Earth. The first is the sun, which gives us energy and warmth. The second are the seas and oceans, which store heat and transport it around the globe via a system of complex global currents. The third is the atmosphere. Without an atmosphere the heat from the sun would mostly reflect back out to space from the surface, and temperature differences between day and night would be much more extreme. Without an atmosphere the UVB radiation that would arrive at the surface directly from the sun would make life on Earth very difficult for current species - including us - to survive.

The atmosphere serves many functions. It effectively holds warmth and radiation from the sun and helps to make our climate habitable. Without the atmosphere, Earth could be on average as much as 59oF colder (33oC) 1.

Below is a table showing the most dominant gases that make up the atmosphere:

Gas Formula Volume %

As we can see from this table, most of the atmosphere is made up of Nitrogen and Oxygen.

The amount of water vapor in the air is variable. It is generally a higher % of the atmosphere in the equatorial regions which is therefore more humid, and the air is much dryer at the poles.

The gases highlighted in bold are greenhouse gases, as explained below.

Nitrogen N2 78%
Oxygen O2 20.9%
Water Vapor H2O 0-4%
Hydrogen & the inert gases - Argon, Neon, Helium H/Ar/Ne/He 0.93%
Carbon Dioxide CO2 0.038%
Nitrous Oxide N2O 0.00003%
Ozone O3 0.000005%

 Greenhouse Gases and the Greenhouse Effect
Some of the gases that make up a small constituent of our atmosphere are known as greenhouse gases. There are also some greenhouse gases found within the atmosphere in much smaller amounts than those listed above. These include methane and chemical compounds called CFCs and HFCs.

The main greenhouse gases are water vapor, carbon dioxide, nitrous oxide and methane (CH4). All of the greenhouse gases can come from both natural and manmade sources, with the exception of some CFCs and HFCs, which are purely anthropogenic and used in aerosols, for instance.

Greenhouse gases have the ability to absorb some of the heat being reflected back up from the Earth and reflect it back down towards the surface again, causing the troposphere - the lowest area of the atmosphere in which all weather occurs - to heat. This is the process is known as the greenhouse effect, and without it we would not be able to survive on this planet.

So greenhouse gases are essentially a good thing - but unfortunately, like so many things in life, too much of a good thing can be bad for us!

The term 'greenhouse effect' is in reality a bit of a misnomer, as the analogy of a greenhouse is not entirely accurate. A glass greenhouse simply traps the heat and prevents the warm air from escaping out. In the atmosphere the gas molecules actually absorb the heat radiation, transform it and then re-emit it, but the term 'greenhouse effect' has stuck. 1



Greenhouse Gas EPAThe graphic to the right (courtesy of EPA) shows a simple version of how this heating process occurs.

Since around the time of the Industrial Revolution in Western countries, concentrations of carbon dioxide, methane, and nitrous oxide in the atmosphere have all risen dramatically.

So, where are all these greenhouse gases coming from?

Carbon dioxide: When we burn fossil fuels, in the form of coal for our electricity, or oil as fuel for our cars, the carbon in the fossilized material that has been locked into the earth for millions of years is released back into the atmosphere in the form of Carbon Dioxide (CO2). According to the NOAA (National Oceanic and Atmospheric Administration), in the past 400,000 years, carbon has never been present above 300 parts per million (ppm) in the atmosphere. As of 2008 it is at 384ppm.

Methane: Methane is a particularly potent greenhouse gas, and is naturally emitted from cattle and from organic matter as it rots away. Major emitters of methane into the atmosphere are landfills, wetlands and rice paddies. Increasingly intensive agriculture, and an expanding global human population have been the primary causes for the increase in anthropogenic methane.

Water vapor: As the air warms, it increases its ability to absorb moisture, as we see regularly when Charlottesville has days of high humidity. As the oceans and the planet surface warm, more water vapor is evaporated from them - leading to more water vapor in the air and an increased warming effect.

Nitrous Oxide: Human induced nitrous oxide primarily comes from burning fossil fuels in cars and other transportation, agricultural soil management and sewage treatment. Nitrous oxide is also produced naturally from a wide variety of biological sources in soil and water.

The issue is not whether the Earth's atmosphere is stable - over long time frames it is not. Various studies have shown many periods of warming and cooling over the Earth's lifetime (about 4600 million years). So climate change is not new. The current issue is that our actions are seriously contributing to, and perhaps wholly causing climate change, and forcing the climate to change at an unprecedented rate - something that naturally may occur over thousands or even tens of thousands of years happening in a matter of decades.

The following groups of national and international organizations have issued state-
ments underscoring that human activities are to blame for the majority of these greenhouse gas increases, and this is resulting in anthropogenic (human caused)
global climate change: the National Academy of Sciences from 21 different countries,
as well as The American Association for the Advancement of Science, the American Meteorological Society, The National Research Council, the National Oceanic and Atmospheric Administration, the American Geophysical Union, the Geological Society
of America, the American Chemical Society, the American Association of State Climatologists, NASA, the World Meteorological Association, the International Council
on Science, and the American Astronomical Society. 

Climate Change - Expected Impacts

According to NASA data, the average surface temperature has increased by about 1.2 to 1.4 degrees Fahrenheit (0.5oC) since 1900. Other aspects of the climate are changing as a result - such as rainfall patterns, snow and ice cover, and levels of humidity.

Decades ago, climate scientists told of the predicted patterns of climate change caused by increasing greenhouse gas concentrations. What they predicted is exactly what we are seeing. Scientists are certain that human activities are changing the composition of the atmosphere, and that increasing the concentration of greenhouse gases will change the planet's climate. If there is uncertainly, then it is regarding the rate that these climate changes will occur, and in the range of the resulting effects.

Most towns and cities will be directly affected, to a greater or lesser degree, because the supply of water, food and other resources on which they depend will be subject to changes in rainfall and other events. Spring is coming earlier and the ranges of many plants and animals are shifting poleward. Species extinction and the bleaching of the world's coral reefs are expected outcomes of even an average temperature increase.

The summer of 2007 caught the attention of most climatologists as melting Arctic ice extent was so dramatic that the Northwest sea passage was open for the first time since satellite observations began in 1978. The picture below is courtesy of NASA; on the left, it shows meltwater rates of the Greenland ice mass. On the right, the red line represents sea ice average from 1979 - 2000. The white sea ice extent shows September 2008 data. 

Picture of Declining Ice Mass

Coastal cities will be most vulnerable to flooding events - not just because of melting land ice on Greenland or in the Antarctic, but because of two other reasons: as the oceans warm, they expand, and freshwater is greater in volume than saltwater. Coastal flooding and conversely water shortage are probably the biggest imminent threats to the US. Just 3 feet of raised water level will have flooding impacts on populations and economies of major coastal cities on the Atlantic and Gulf coasts, as well as making coastal cities & towns much more susceptible to damage from tidal surge in storm events. Rising sea levels could be a massive problem globally, as over one third of the world's population live within 33 feet of sea level. Storm surge and tidal push inland from higher seas will also interfere with these populations' freshwater aquifer supplies.

What about Virginia?

For most people in the US, climate change so far has made little difference in daily life. Heating bills may go down, but air conditioning bills may go up. In the US, more northern areas may see an extended growing season, while southern areas' overall increase in temperature may affect what crops farmers can successfully grow. Although hurricanes receive the main headlines, other events that are likely to occur include an increase in the duration and quantity of heat waves. This will impact power requirements for air conditioning, water management, and health services.

The IPCC (UN Intergovernmental Panel on Climate Change) estimates that the global average sea level will rise between 0.3 and 2.9 feet in this century if current emissions continue. As for specific impacts to Virginia – most notably at this stage is the affect on low lying coastal areas and the Chesapeake Bay area, which is already suffering from pollution and wetland loss. The Governor's Commission on Climate Change Report states that many of the Chesapeake Bay's foundation species could decline or disappear altogether as salinity and temperature increase. Military installations at Norfolk and merchant operations in the Newport News area could also be negatively impacted. The report also notes that climate change will "exacerbate threats already faced by Virginia ecosystems, such as invasive species, pathogens, and pollution" (p.5).

Moderate emission scenarios cited in the Governor's Report forecast the average warming for Virginia to be 5.6 degrees F and precipitation to increase by 11%.


What can we do about it?

'While it may be a bit of a reach to think in terms of "Saving the Planet" from global warming, it's perfectly valid to think about preserving a climate that's sustaining to as many of Earth's residents as possible' 2

Even if carbon dioxide and methane emissions stopped entirely today, climate change will still continue due to the length of time that both compounds remain present in the atmosphere, and due to the lag heat effect in oceans and ice. However, the catastrophic effects in the coming century and beyond would be substantially lessened (IPCC 2001).

In June 2007, the City conducted a greenhouse gas emissions baseline report, for both the community and the government sectors. This baseline is an inventory of the activities within our community that add to our greenhouse gas emissions. Establishing an overall tonnage of emissions enables us to set quantifiable and realistic targets for reducing our emissions for both now and in the future. The emissions inventory is an analysis of City residential, commercial, industrial, transportation and waste sectors; as well as an analysis of municipal buildings, facilities and operations.

In 2008 Charlottesville began the process of building consensus for a Local Climate Action Planning Process (LCAPP). 2009 saw the formation of a Steering Committee for that plan, as well as technical working groups to focus on specific components of the plan. The group continues to work to arrive at recommendations for community actions to reduce greenhouse gas emissions.

  • Individually, conservation and energy efficiency is key. For tips on energy efficiency in the home, please CLICK HERE
  • For details on recycling, please CLICK HERE
  • For details on water conservation, please CLICK HERE
  • Calculate your carbon emissions and get tips on how to reduce them, please CLICK HERE

1 Breenan and Withgott; Environment; Pearson 2005

2 Henson; Guide to Climate Change; 2006