Environment and Climate Change

Background on Climate Change

The contribution of greenhouse gases (GHGs) such as carbon dioxide (CO2), methane and water vapour to the ‘greenhouse effect’ that raises the earth's temperature to habitable levels was demonstrated by John Tyndall in 1859. In the 1890s, the Swedish scientist Svante Arhennius calculated the effect of doubling atmospheric CO2 to be an increase of global temperatures of around 5 °C (broadly in line with current estimates).

Emissions of CO2 rose by a factor of 16, to around 35 billion tonnes per annum, between 1900 and 2008 (US Environmental Protection Agency data). Polar ice records show that the long-run variation over the 740,000 years prior to the industrialized period had been between 180 and 280 parts per million (ppm). In the spring of 2013, the concentration of CO2 passed 400 ppm. When the contribution of methane and other GHGs is added, the effective concentration is higher still. Climate policy appears to have had little or no effect on this trend.

These increases in atmospheric CO2 come from increasing use of fossil fuels, deforestation and also agricultural practices. There is reason to expect some ‘feedback effects' (e.g. the release of methane from beneath the Russian tundras) that could suddenly accelerate warming. Some opposing feedback effects (e.g. if cloud cover were to increase the reflection of radiation from the sun) are also likely. Nonetheless, there is broad consensus that increases of between 2 and 4 °C in temperature are likely within the twenty-first century; that these will have serious consequences on the well-being of humans, on economies and on ecosystems and that the greater the warming, the more serious the impacts will be.

The water cycle will be particularly affected by climate change (e.g. by floods and droughts), with knock-on impacts on the design of buildings, on agriculture and in many other economic and social areas. The impact of temperature on ecosystems is likely to be very significant as species travel towards the poles (or to higher elevations) at differing speeds, risking what the UK scientist Sir John Lawton called ‘unravelling the fabric of nature’.

Climate policy addresses two concurrent and urgent transformations: (1) adaptation (adapting human and natural systems for the climatic changes that are expected and that may already have begun) and (2) mitigation (reducing emissions of GHGs and other ‘forcing activities' so as to stabilize temperatures). Both are essential: adaptation because delays in the climate system mean that climate change will continue for decades, even if all emissions were to stop tomorrow, and mitigation because changes much beyond 2 °C may be beyond our species' capacity to cope.

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