Download Increasing severity of the consequences of climate change Human

. Increasing severity of the consequences of climate change
Human induced climate change is driven mostly by GHG emissions from fossil fuel
use for energy, but also by deforestation and unsustainable agricultural practices. It
can be viewed as a driver of environmental change in its own right, as it affects the
direction and magnitude of other trends and indeed megatrends. Aspects covered here
include impacts on crop production, water availability, an biodiversity, as well as
oceanic acidification.
The concentration of atmospheric CO2 has increased from about 280 ppm in preindustrial times to more than 387 ppm in 2008i. As a consequence, the average global
air temperature by 2009 had risen by 0.7-0.8 °C. Current projections suggest global
mean temperatures could rise by as much as 1.8-4.0 °C over the course of this century
if global action to limit GHG emissions proves unsuccessful.ii
Figure 1. Impact of climate change (including CO2 fertilization effect) on agricultural yields (% change)
Although global crop production may increase initially (before 2030), globale
warming is projected to have negative effects in the long run. Whereas crop
production in high latitude regions will generally benefit from climate change,
agricultural production and access to food in many African countries and Latin
America is projected to be severely compromised (Figure 1).iii iv
Water availability in different parts of the world may be severely affected by climate
change. Many drylands are projected to become even drier and water demand will
increase in all regions, because of larger evapotranspiration caused by higher
temperatures. Furthermore, climate change may cause extreme weather events
(including droughts) to occur more frequently and with greater intensity, increasing
risks and uncertainty in food production (Figure 2).4
Figure 2. Projected climate change impacts on freshwater between 1981-2000 and 2081-2100.
Background shows ensemble mean change of annual runoff, in percent
Source: IPCC, 2007
Climate change also affects biodiversity. Boreal forest and Arctic tundra ecosystems
are projected to increase due to longer and warmer growing seasons. Vegetation
change in the lower to mid latitudes is uncertain because transitions between tropical
desert and woody vegetation types are difficult to forecast. A general increase of
deciduous at the expense of evergreen vegetation is predicted at all latitudes (Figure
3).4 These general effects of climate change can be masked to some extent, since
potential natural vegetation is often modified heavily by humansv.
Figure 3. Projected climate-induced changes in terrestrial ecosystems by 2100 relative to 2000.
Two SRES scenarios and climate models: (a) HadCM3 A2, (b) ECHAM5 B1
Source IPCC, 2007b
The increasing accumulation of CO2 in the atmosphere is also important for marine
ecosystems, as it increases ocean acidity. Organisms producing shell and skeletal
constructions of calcium carbonate are expected to be especially vulnerable. Coral
species, for example, may go extinct within the next century if atmospheric CO2
concentrations continue to rise unchecked (Figure 4).vi
Figure 4. Modeled change in growing conditions for warm water coral reefs between approx. 1870 and 2065.
Source WGBU 2006
Why is it important?
Climate change influences the Earth’s surface temperature, the sea level and the
amount, timing and intensity of precipitation. On land, these changes affect freshwater
availability and quality, surface water run-off and groundwater recharge, and the
spread of water-borne disease vectors. Extreme weather conditions have an
increasingly large impact on vulnerable human communities, particularly the world’s
poor. In some cases, climate change has severe effects on human health, food
production, security and resource availability. The consequences for society are
reduced water and food security, increased health risks and increased potential for
societal tension and regional conflicts. The relative importance of climate change
compared to the other megatrends is projected to increase towards the latter part of the
21st century. While population growth as a key driver is slowing down, the full
consequences of climate change may only become visible in a few decades.
The projected climate change has far-reaching impacts in Europe including
temperature increases, sea-level rise, changes in precipitation patterns and water
availability, and more frequent and intense extreme weather events. Climate change
will affect the vulnerability of European society to an array of threats to human
health, almost all economic sectors, ecosystem goods and services and biodiversity.
Vulnerabilities differ across regions, sectors and communities, with pronounced
consequences expected in the Mediterranean basin, North-Western Europe and the
Arctic. Many coastal zones, mountains and areas prone to river floods are particularly
vulnerable, as are cities and urban areas. In some sectors and regions new
opportunities may occur. However, with increases in both temperatures and the
frequency and intensity of extreme weather events, adverse effects are likely to
dominate in the medium to long term.
Key drivers and uncertainties
Increases in GHG emissions are largely due to the use of fossil fuels, although
deforestation, land-use change and agriculture also provide significant but smaller
contributions. Major drivers are therefore global population growth, increases in
demand for food, water and energy, and agricultural practices. Policy responses, both
in terms of mitigation and adaptation, are crucial.
The uncertainties regarding GHG emissions and ecosystem responses (actual climate
change, sea level rise, ecosystem vulnerability and tipping points) are considerable.
Major uncertainties remain also at the level of impacts on human society, including
long-term health effects, regional conflicts, migration and political instability.
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Richardson, K., Steffen, W., Schellnhuber, H.J., Alcamo, J., Barker, T., Kammen, D.M., Leemans, R.,
Liverman, D., Munasinghe, M., Osman-Elasha, B., Stern, N. and Wæver, O. (2009). Synthesis Report.
Climate Change, Global Risks, Challenges and decisions, report from Copenhagen conference March, 2009.
http://climatecongress.ku.dk/
IPCC, 2007. Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the
Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, Pachauri,
R.K and Reisinger, A. (eds.)]. IPCC, Geneva, Switzerland, 104 pp.IPCC, 2007, Synthesis report
IPCC (2007b). Climate Change 2007: Impacts, Adaptation and Vulnerability, Contribution of Working
Group II, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., IPCC,
Geneva, Switzerland,
Cline, W.R. (2007). Global Warming and Agriculture. Finance & Development. 23-27.
Ellis C.E., Ramankutty N. (2008): Putting people in the map: anthropogenic biomes of the world, Front Ecol
Environ, 6, 8, 439-447
WBGU (2006): The future oceans – warming up, rising high, turning sour, special report of the German
Advisory Council on Global Change, Berlin, Germany