|Definition of Global Warming: Gradual increase in the earth’s surface temperature.
Popular usage definition: Warming caused by human activity.
Technical term for this: Anthropogenic global warming.
Definition of Greenhouse Gas: A gas, like CO2, which traps the sun’s heat.The debate: Is the observed global warming natural or man made?
Human causes: Carbon dioxide (CO2), e.g. exhaust from cars and power plants.
U.S. Government Position: The Energy Act of 2005 states: “the President shall establish a Committee on Climate Change Technology [which] shall submit to the Secretary and the President a national strategy to promote the deployment and commercialization of greenhouse gas intensity reducing technologies and practices.”
History: In 1896 Svante Arrhenius (1903 Nobel Prize in Chemistry) predicted the decrease in CO2 needed to cause past ice ages. He wasn’t far off, and it is not a large decrease. This helped confirm the 1859 prediction that human-produced increases in CO2 would cause just the reverse: global warming.
What Causes Global Warming, human activity or the sun? The final answer is not in, but you can see the results so far. (1) Exhaust is clearly the source of CO2. (2) Everyone now agrees the earth is warming. (3) Decide for yourself if warming is better explained by CO2, or the sun’s heat.
The Effects of Global Warming. We can see the long-term effects coming in the melting of polar ice and glaciers. But a powerful trend in Atlantic hurricane data indicates we can already see the impact. Katrina was partly the result of a normal weather cycle, but that cannot explain away stronger hurricanes world wide.
Can we Stop Global Warming?
The phrase global warming refers to the documented historical warming of the Earth’s surface based upon worldwide temperature records that have been maintained by humans since the 1880s. The term global warming is often used synonymously with the term climate change, but the two terms have distinct meanings. Global warming is the combined result of anthropogenic emissions of greenhouse gases and changes in solar irradiance, while climate change refers to changes caused by global warming in weather (temperatures, precipitation, frequency of heat waves, etc.) and other climate system components, such as Arctic sea ice extent.
The United States National Climatic Data Center (NCDC), found that in 2006 “Globally averaged land temperatures were +0.78°C (+1.40°F) and ocean temperatures +0.45°C (+0.81°F) above average, ranking 4th and 5th warmest, respectively. The land and ocean surface temperatures for the Northern and Southern Hemisphere ranked 2nd and 6th warmest, respectively,” since global temperature record monitoring began in 1880. The NCDC report states that “during the past century, global surface temperatures have increased at a rate near 0.06°C/decade (0.11°F/decade) but this trend has increased to a rate approximately 0.18°C/decade (0.32°F/decade) during the past 25 to 30 years. There have been two sustained periods of warming, one beginning around 1910 and ending around 1945, and the most recent beginning about 1976.”
The NCDC’s Preliminary Annual Report on the Climate of 2007 (released December 13, 2007) states that:
- “the global annual temperature for combined land and ocean surfaces for 2007 is expected to be near 58.0°F and would be the fifth warmest since records began in 1880,” and that
- “the year 2007 is on pace to become one of the 10 warmest years for the contiguous U.S., since national records began in 1895.”
The NCDC 2006 report also described temperature trends aloft in the atmosphere measured over the past 50 to 60 years using balloon-borne instruments (radiosondes) and for the past 28 years using satellites. The report states that temperature data collected from approximately 5,000 to 30,000 feet above the surface indicate that 1958-2006 global temperature trends in the middle troposphere are similar to trends in surface temperature; 0.12°C/decade for surface and 0.15°C/decade for mid-troposphere.
On 2 February 2007, the Intergovernmental Panel on Climate Change (IPCC) released the Summary For Policymakers (SPM), an executive summary of the first volume of its 4th Assessment Report entitled, “The Physical Science Basis of Climate Change.” The IPCC Report documents that not only do the records show a warming trend during the past half century in land-based temperature data but also in global ocean temperature measurements. The increases in ocean temperatures indicate global warming trends are not an artifact of urbanization or the so-called “heat-island” effect.
The NCDC Report also documents not only a long-term warming trend for the globe as a whole but also a warming trend for the contiguous United States. The Report documents that the 2006 average annual temperature for the contiguous U.S. was the warmest on record and nearly identical to the record set in 1998.
Causes of Global Warming
In the IPCC Fourth Assessment Report scientists conclude that “warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level” and, furthermore, they conclude with “very high confidence (at least a 9 out of 10 chance of being correct) that the globally averaged net effect of human activities since 1750 has been one of warming” of the Earth’s climate system.
As with every environmental variable, there are multiple factors that contribute to the “warmth” of the Earth. Humans measure warmth as temperature which is a measure of the amount of heat contained in a physical object. One can envision this concept by thinking of a pot on a stove. As heat is applied to the pot from a flame or heating element, the temperature of the pot will increase. But heat will also begin escaping the pot in the form of steam and also through radiative and convective cooling from the top and the sides of the pot. Eventually the rates of both heat loss (cooling) and heat gain (warming) may stabilize and the heat then contained within the pot at an instantaneous point of time would be reflected in an equilibrium temperature. This equilibrium temperature could be measured directly but it also could be calculated by determining all of the flux rates of heat entering (heating) and leaving (cooling) the pot.
One way that climate scientists look at the warmth of the Earth’s climate system is to calculate the annual average temperature of the surface of the Earth using temperature measurements systematically collected throughout the year from thousands of land- and ocean-based weather and observation stations. The observed trends in the Earth’s annual average temperature is one of the factors leading to the scientific conclusion that the Earth is now in a period of global warming.
In order to attempt to answer why the Earth is currently warming, scientists have conducted accountings of each of the fluxes of heat into (warming) and out of (cooling) the Earth’s climate system. Since the measured data show that annual average temperatures of the Earth have been increasing in recent decades, the year-to-year annual flux of heat into the climate system must be greater than the annual flux of heat out of the system. By accounting for each of the fluxes of heat into and out of the system, scientists are able to assess which fluxes and processes are contributing to net annual warming of the Earth’s surface. By conducting such accountings, scientists are able to quantify the influence that each natural and human factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system and can calculate an index of the importance of each of the factor as a potential climate change mechanism. Each of the factors are called climate drivers and the relative impact or index of each factor’s importance to climate change is called its radiative forcing.
In completing such an assessment, the IPCC has concluded with very high confidence that the globally averaged net effect of human activities since 1750 has been one of warming. The scientists found that the combined radiative forcing due to increases in carbon dioxide, methane, and nitrous oxide is the largest climate driver and its rate of increase during the industrial era is very likely to have been unprecedented in more than 10,000 years. Furthermore, the carbon dioxide radiative forcing increased by 20% from 1995 to 2005, the largest change for any decade in at least the last 200 years.
The IPCC also found that anthropogenic contributions to aerosols in the atmosphere produce cooling effects, referred to as global dimming. However the cooling (global dimming) effects due to human-caused aerosols are equivalent to about half of the warming effects due to the combined radiative forcing of human-produced greenhouse gases, causing a net warming.
Significant anthropogenic contributions to radiative forcing were also found to have come from several other sources, including tropospheric ozone changes due to emissions of ozone-forming chemicals, direct radiative forcing due to changes in halocarbons, and changes in surface albedo, due to land-cover changes and deposition of black carbon aerosols on snow. However the impacts of each of these factors was relatively small compared to the impacts of anthropogenic greenhouse gases (each showing relative impacts of 15% or less relative to the greenhouse gas forcings).
Finally, an increase in solar irradiance since 1750 was estimated to have caused a forcing that contributed to the recent warming of the Earth. However, the impact of the increase in the amount of sunlight striking the Earth each year during this ~250 year time span was estimated to be only about 1/20th of the warming impacts of anthropogenic greenhouse gas emissions.
Climate change refers to the variation at a global or regional level over time. It describes the variability or average state of the atmosphere or average weather over time scales ranging from decades to millions of years. These variations may come from processes internal to the Earth, be driven by external forces (e.g. variations in sunlight intensity) or, most recently, be caused by human activities.
If you are not sure of the difference between ‘climate’ and ‘weather’, click on the link to find out: Climate-Weather.
No time to read all this? For a quick one page summary on the Facts and Impacts go
hereor listen to four scientists from Columbia University explain future climatic uncertainties. With Peter DeMenocal, Gavin Schmidt, Maxx Dilly and Klaus Lackner.
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Just as weather patterns change from day to day, the climate changes too. This occurs naturally, driven by internal and external factors. However not all changes are due to natural processes, as we humans have also exerted our influence ( anthropogenic climate change). Through widespread use of land, and the building of cities, we have changed our climate. The major technological and socioeconomic shift of the industrial era with reduced reliance on organic fuel, the accelerated uptake of fossil fuels, and broad scale deforestation, means we have contributed to the natural greenhouse effect.
The key areas for concern are those related to variability and extremes, not simply changed average conditions. There is an accumulating body of evidence of observed impacts relating to regional changes, and that these are having fearful effects on the world around us.
There are already people who have become climate refugees, and millions more are expected in the future. Temperatures across the globe are most certainly rising; the 1990s was the warmest decade in the last thousand years. Sea surface temperatures have increased 0.4-0.8°C (0.7-1.4°F) since the late 19 Century, and over the period 1961 to 2003, global ocean temperature has risen by 0.10°C (0.18°F) from the surface to a depth of 700 m.
The world has warmed 0.74°C in the past hundred years and scientists are clear that the world will get warmer this century due to further increases in greenhouse gas concentrations. Global average temperature is forecast to rise 4°C (7.2°F) toward the end of the 21st century. Warming of a few degrees seems inconsequential compared with day to day, or seasonal variations in temperature. However, in global terms it is much larger than any of the climatic changes experienced during the past 10,000 years, since the rise of agriculture and civilisations. Although the Earth has seen many climatic changes during its 4.6 billion year history, the current changes are spurred by the human burning of fossil fuels.
In addition to warming of the Earth’s surface, there has been an increase in heatwaves, warming of the lower atmosphere and deep oceans. There are fewer frosts, permafrost is melting, glaciers are retreating and sea ice is decreasing. Sea levels have risen 10–20 cm and there is increased heavy rainfall in some regions, and less in others.
Climatic changes over recent decades have already affected some health outcomes. The World Health Organisation estimated, in its “World Health Report 2002”, that climate change was estimated to be responsible in 2000 for approximately 2.4% of worldwide diarrhoea, and 6% of malaria in some middle-income countries. Epidemics of weather and climate-sensitive infectious diseases such as malaria and meningitis will have a devastating effect on human health and socio-economic development and severely overburden health systems in many parts of the world.
The Fourth Assessment Report released in 2007, by the Intergovernmental Panel on Climate Change (IPCC) stated that “there is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities”. As seen below, The Report also shows why there is cause for deep concern:
Hydrology and Glaciers – Glaciers are retreating, and snow cover is decreasing (e.g. Davos in the Swiss Alps) with earlier snowmelt, and changing snow ecology. There is also reductions in the annual duration of lake and river ice.
Sea Ice – Declining sea-ice extent and thickness.
Animals – Poleward and elevational shifts in range, and alteration in species abundance (e.g. Sea Turtles ). Over a million species are predicted to become extinct by 2050 (e.g. Boyd’s Forest Dragon, Cassowaries ). Changes in phenology (including earlier reproduction and migration), physiological and morphological adaptation.
Plants Change in abundance, diversity, and range, change in phenology (including earlier flowering), change in growth.
The Australian Government, whilst not signing the Kyoto Protocolhave acknowledged, “The projected global warming of a few degrees in the 21st century would occur at a time that is already one of the warmest for hundreds of thousands of years, with current levels of carbon dioxide not exceeded for the past 420,000 years, and not likely during the past 20 million years”.
A few degrees of global warming will lead to more heat waves and fewer frosts. More wildfires and droughts are expected in some regions of the world with higher rainfalls and resultant flooding in other areas. Higher latitudes of the globe would receive more rainfall while middle latitudes, including parts of Australia, are likely to receive less. For these areas the changes will pose significant problems for water resource management.
Tropical hurricanes and cyclones may become stronger and sea level may rise 9 to 88 cm by the year 2100. Some low-lying coastal areas and islands could be more prone to inundation from storm surges. Human induced climate change is another major stress in a world where natural and social systems are already experiencing pollution, increasing resource demands and unsustainable management practices.