- 71% of the Earth is covered by its ocean.
- 60% of the heat from the Equator is moved polewards by ocean currents.
- Glaciers and ice caps currently store ~0.5 m of sea level equivalent, and their current mass loss contributes ~1 mm/yr to sea level rise. This is approximately equal to the combined contributions from ice sheets in both Greenland and Antarctica.
- Arctic sea ice has lost nearly half its average summer thickness since 1950 and by mid-century it may disappear completely in the summer for the first time in over 1 million years.
- Climate change could kill more than a third of the world's plant and animal species by 2050.
- At some higher latitudes the growing season is now more than two weeks longer than it was in the 1950's.
- According to the 2007 IPCC report, the global average temperature is likely to rise anywhere from 1.1°C to 6.4 °C by 2080-2099, relative to 1980-1999.
Frequently Asked Questions
One of the primary sources of information about the climate and current climate change research are the Assessment Reports from the Intergovernmental Panel on Climate Change (IPCC). These reports are written by teams of scientists and contain clear facts about what is happening. The following excerpts are taken from the most recent Fourth Assessment Report, published in 2007:
If Emissions of Greenhouse Gases are reduced, how quickly do their concentrations in the Atmosphere decrease?
- A complete cut-off in emissions would lead to a return to pre-industrial revolution concentrations for gases such as CH4, HCFC-22 and halocarbons (gases with a lifetime of around a decade) within a century.
- Atmospheric gases with longer lifetimes, slow removal processes and complex interaction processes, such as CO2 with its ocean-atmosphere gas exchange, chemical weathering release and biological release (photosynthesis), would initially respond to a 50% cut by stabilising at current levels for less than a decade before increasing again as slow releasing land and ocean sinks begin to adjust.
How do human activities contribute to climate change?
- CO2 levels have risen due to burning of fossil fuels, deforestation and decay of plant matter.
- Methane increased due to the rise in agriculture, natural gas distribution and landfills, However, methane levels in the atmosphere are not currently increasing due to growth rates decreasing over the last two decades.
- Nitrous oxide (N2O) is emitted through fossil fuel burning and use of fertilisers, as well as via naturally occurring processes in the soils and oceans.
- Halocarbon gases, including chlorofluorocarbons, were extensively used in manufacture and industrial processes. However, international legislation to protect the ozone layer has resulted in a decrease of these gases in the atmosphere.
- Water vapour, as the most abundant greenhouse gas, can be indirectly affected by humans due to changes in the climate. As the climate gets warmer, there is more water vapour in the atmosphere.
- Ozone is a gas that is created and destroyed in the atmosphere due to chemical reactions. Human activities have led to an increase in carbon monoxide, nitrogen oxide and hydrocarbons, all of which react to produce ozone.
- Feedback mechanisms amplify the effects of some greenhouse gases. For example an increase in CO2 increases the greenhouse effect and so warms the Earth. This in turn creates a warmer and wetter atmosphere, resulting in the formation of more water vapour, which has the ability to more than double the greenhouse effect of the initial CO2 input.
How are temperatures on Earth changing?
- Between 1906 and 2005, global average surface temperatures have increased by 0.74°C.
- 1850 – 1915 saw mainly natural variability.
- 1910’s – 1940's saw an increase of 0.35°C before a slight cooling of 0.1°C.
- 1940’s – 2005 saw a rapid warming of 0.55°C.
- Warming has generally been greater over the land than the oceans, and seasonally, winter has seen the greatest warming effects.
Is the amount of snow and ice on the Earth decreasing?
- Sea ice in the Arctic is shrinking in all seasons, but most notably in the Summer. Satellite measurements since 1978 show a decrease of 2.7 ±0.6% per decade annually, with a Summer decrease of 7.4 ±2.4% per decade.
- Northern Hemisphere spring snow cover has declined by 2% per decade since 1966, despite increases in precipitation in some places.
- Submarine data for the thickness of Antarctic sea ice suggest local thinning of up to 40%, although this is considered an over-estimate of thinning across the entire region.
- Melting of glaciers and ice caps contributed 0.77 ±0.22 mm yr-1 to sea level rise between 1991 and 2004.
- Thickening of high-altitude regions of Greenland and Antarctica due to increased precipitation has been more than offset by thinning and loss at the coastal regions due to increased ice outflow and surface melting.
Is Sea level rising?
- Global sea level rose approximately 120m following the end of the last Ice Age, stabilising around the UK ~5,000 years ago. Records then show sea level begin to rise at ~1.7 mm yr-1 during the late 19th Century. However, satellite records since 1993 suggest that this has increased to ~ 3 mm yr-1, with thermal expansion of the oceans due to warming, and melting of the land ice each accounting for ~50% of this figure.
- Sea level rise is not uniform throughout the world, with some places showing sea level fall. This spatial variability is due to changes in the ocean’s temperature, salinity and circulation patterns.
- Model projections suggest that sea level rise could reach ~4 mm yr-1 by the mid 2090’s, with actual sea levels 0.22 to 0.44m above the level measured in the 1990's.
Source: IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.