Climate Change Impacts
Climate change’s biological impacts: Effects of global warming on ecosystems, agriculture, and human health
This briefing note is aimed at biologists, policy makers and the interested public. It summarises the predicted impacts of global warming on areas of particular interest to biologists: ecosystems, agriculture and human health.
We have not attempted to review the relevant literature, but have based the note on the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), published in 2007. This means that the data have had the benefit of rigorous review by the world’s experts, but are inevitably out of date.
More recent predictions can be found in an interactive map and on the Met Office Hadley Centre website.
Our climate is changing, and the driving force for this change is human activity and our emission of greenhouse gases, for example through fossil fuel burning and agriculture. Carbon dioxide emissions have increased by 80% since 1970, and grown massively since 1750: the date taken as the pre-industrial reference point by IPCC [1]. Global average temperatures have risen by around 0.8oC since then. These trends are set to continue to accelerate in the 21st century. Changes in carbon dioxide levels and temperature alter the climate by affecting weather systems, water, land and living organisms.
Global temperatures have fluctuated in the past, resulting in major changes to the Earth’s climate. Such changes have usually been much slower than those now seen (often occurring over thousands of years, not decades), but have still been catastrophic. Indeed, Earth’s previous mass extinctions have all been due to climate change. The same holds true today: terrestrial and marine ecosystems have little chance to adapt to a rapidly changing climate, and many plant and animal species face extinction as their habitats are lost to climate change. Marine ecosystems face the additional threat of ocean acidification, as carbon dioxide dissolves in the water.
The IPCC report states: “The resilience of many ecosystems (their ability to adapt naturally) is likely to be exceeded by 2100 by an unprecedented combination of change in climate, associated disturbances (e.g., flooding, drought, wildfire, insects, ocean acidification), and other global change drivers (e.g., land-use change, pollution, over-exploitation of resources).”
Human health and agriculture will also be impacted by rising atmospheric carbon dioxide levels and temperatures. Climate change currently contributes to the global burden of disease and premature deaths. Global food production potential is likely to increase with increases in global average temperature up to about 3.6°C, but above this it is very likely to decrease [2].
The IPCC’s fourth assessment report suggested that global average temperatures may rise by between 2 and 6.8oC this century, depending largely on the extent of continued greenhouse gas emissions. Below is a summary of the key trends of the future of ecosystems, agriculture and human health at up to 2oC and up to 5oC rises in global average temperature since 1750. Many of these trends are becoming apparent already. Few authors have published papers on the impacts of a temperature increase above 5oC, but it is clear that these would be even more severe.
The UK government hopes to achieve a new international climate agreement in Copenhagen in December 2009, to limit global temperature increases to no more than 2oC and avoid the most dangerous effects of climate change. Their policy is here.
The IPCC’s studies express uncertainty in the data in terms of the temperature range at which an event can be expected to occur, and a percentage range to express uncertainty in the severity of the event. They also consider a number of alternative futures, depending on whether or how fast we act to reduce greenhouse gas emissions. We refer the reader to the IPCC’s report and its technical summary to gain a full picture of these important caveats.
Consequences of a 2 oC rise in global average temperature:
- Coral reef bleaching
- More frequent and intense wildfires
- Severe weather events
- Ocean acidification [3]
- Substantial habitat loss: freshwater, rainforest, polar regions, vulnerable island ecosystems
- Substantial species loss globally, and geographical range shift and loss
- Crop yield increases at high latitudes, but decreases at low latitudes
- Forest expansions in North America and Eurasia
- Tropical forests likely to experience severe impacts including biodiversity losses.
- More heat-related, fewer cold-related deaths
Consequences of a 2 to 5 oC rise in global average temperature:
- Terrestrial biosphere becomes a net carbon source
- Coral reef mortality
- Extreme weather events: heat waves, flooding, drought, storm surges
- Glacial retreat by 50%
- Sea level rise by several metres due to Greenland ice sheet loss [4]
- Sea level rise by 1.2m due to thermal expansion of oceans
- Substantial habitat loss: tundra, rainforest, alpine (including cloud forest)
- Increase in infectious and cardio-respiratory diseases
- Mortality from heat waves and extreme weather events
- Substantial burden on health services
- 40-70% of species committed to extinction
- Crop yield reduced in all regions.
- Livestock experience heat stress
Specific predictions for Europe: 2 to 5oC rise in global average temperature
· Species loss across most of Europe, and geographical range shift
· Seal, dolphin, amphibian and reptile habitat loss
· Summer temperature increases: up to 6oC in Southern Europe
· Increased drought and wildfires in Southern Europe
· Increased flooding in Northern Europe, flash flooding in urban areas
· Sea level rise by 1.2m: land loss, flooding, salinisation of groundwater
· Loss of 50% of glaciers, increased rockslides and avalanches
· Alpine plant species loss up to 60%
· Crop productivity: increased in North, reduced in South
· Increased mortality from heat-waves and extreme weather events
· Increased respiratory infections, Lyme disease, pollen allergy
· Increased incidence of food poisoning in UK
We rely on ecosystems to provide goods and services – such as clean air and water, soil, food, fibre, nutrient cycling, disease regulation – and without these services humans would not be able to exist on earth. Ecosystems are already under stress from factors distinct from climate change, such as over-exploitation, environmental pollution, and changes in land use such as urbanisation, agricultural intensification and deforestation. Climate change will further affect the ability of ecosystems to provide services. A sustainable balance must be achieved where humans can benefit from the services ecosystems supply, but do not contribute further to their depletion, degradation or destruction.
In addition to ecological, agricultural and health effects, there will be severe economic consequences of climate change. The Stern review on the economics of climate change, commissioned by the UK Treasury in 2006, reported that the cost of doing nothing to mitigate climate change will have severe consequences on the global economy, including the UK. A 2-3oC increase in global average temperature is predicted to cause a 0-3% permanent loss in global output – gross domestic product (GDP). A 5-6oC temperature rise will cause a 5-10% loss in world GDP. To put this in the context of the current financial crisis and its severe impacts on the economy, the International Monetary Fund predicted a modest global GDP increase of 0.5% for 2009, which is expected to recover to above 2% in 2010. The cost of implementing climate change mitigation and adaptation policies is estimated at 1% of global GDP annually. The Stern review concludes that ‘the benefits of strong, early action on climate change outweigh the costs’ and that it is not too late to avoid the worst impacts of climate change if strong action is taken.
Where are we headed? What temperature rise is already inevitable? Temperature has already increased by around 0.8oC since pre-industrial times, and some effects of climate change are already apparent. If we continue on a ‘business as usual’ trajectory of greenhouse gas emissions, by 2050 the global average temperature may increase by 2-3oC, and 5-6oC by the end of the century. The examples above show why we should act urgently to ensure that this does not happen, and that we must prepare to adapt to the climate change to which we have already committed the planet.
The Intergovernmental Panel on Climate Change (IPCC) is a scientific intergovernmental body established by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP). It is tasked with providing an objective source of information about human-engendered climate change to policy-makers. Comprising over 2000 of the world’s leading scientists in the field, it analyses and synthesises global peer-reviewed scientific, technical and socio-economic literature in the field, and also those elements relevant to its observed and projected impacts, and options for adaptation and mitigation. It reports intermittently: the fourth report being released in 2007, with the fifth due in 2014.
Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 976pp. (chapters 4, 5, 8, 12).
Stern Review on the Economics of Climate Change
Millennium Ecosystem Assessment
Avoiding Dangerous Climate Change, Defra
Six Degrees: our future on a hotter planet, Mark Lynas, Fourth Estate Ltd (2007)
[1] All global temperature changes in this note are expressed relative to1750 unless otherwise stated. To express the temperature change relative to 1990 levels, subtract 0.6°C.
[2] IPCC fourth assessment report: Working group II technical summary
[3] Acidification is caused by atmospheric CO2 dissolving is sea water, not by temperature changes.
[4] For Greenland, the temperature threshold for breakdown is estimated to be about 1.7 to 4.4°C above preindustrial global average temperature. This is likely to happen by 2100. Complete melting would occur over centuries to millennia.
Further information
Sea level rise, POSTnote 363, Septermber 2010
Ocean acidification, POSTnote 343, October 2009
Biodiversity and Climate Change, POSTnote 341, October 2009
Arctic changes, POSTnote 334, June 2009
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