Sunday :: Apr 8, 2007

impacts, adaptation, and vulnerability

by Christina Hulbe

The second Intergovernmental Panel on Climate Change Fourth Assessment working group, Impacts, Adaptation, and Vulnerability released its summary for policy makers Friday (pdf). The full 20-chapter report will be released later this year. Video of the press conference that accompanied release of the summary is also available (wmv).

The statement issued Friday outlines observed impacts of global warming, who (and what) is vulnerable to future change and why, and includes a brief discussion of key points related to adaptation and mitigation strategies. One future impact that I'd like to report on the front page because it has been discussed recently here is carbon uptake by the terrestrial biosphere:

Over the course of this century, net carbon uptake by terrestrial ecosystems is likely to peak before mid-century and then weaken or even reverse, thus amplifying climate change. (Assuming continued greenhouse gas emissions at or above current rates.)

Uncertainties in this projection are significant but published research points in the direction of declining carbon uptake as global temperatures and atmospheric CO2 continue to rise ( abstract for a recent study published in Climatic Change and a technical paper pdf ).

Here are a few key points (read the summary (pdf) for more):

observed impacts

  • increasing ground instability due to thawing permafrost
  • changes in sea-ice biomes and predators high in the food chain

water resources

  • increased run-off and earlier spring peak discharge in glacier- and snow-fed rivers
  • warming lakes and rivers with impacts on water quality and ecosystems

terrestrial ecosystems

  • earlier spring events such as leaf unfolding and bird migration
  • poleward & upward shifts in plant and animal species ranges

marine & freshwater ecosystems

  • range and abundance shifts in high-latitude oceans
  • range changes and earlier migration of fish in rivers

settlement & society

  • heat-related mortality
  • increase in allergenic pollen in high and mid-latitude northern hemisphere
  • alterations in disturbance regimes of forests due to fire and pests
  • earlier spring planting of agricultural crops in northern hemisphere higher latitudes

future impacts
water resources

  • 10 to 40% increase in high-latitude and wet tropical river runoff by mid-century
  • 10 to 30% decrease in dry mid-latitude and tropical river runoff by mid-century
  • decline in water supplies from glaciers


  • the coping range of many ecosystems is like to be exceeded due to combined effects of global warming, disturbances associated with warming, and anthropogenic disturbances
  • net carbon uptake by terrestrial ecosystems is likely to peak before 2050 and then decline

food, fiber & forests

  • crop productivity will increase slightly at mid- to high-latitudes for warming between 1 and 3 degrees Celsius and decline for warming beyond that
  • crop productivity is expected to decline at lower latitudes
  • increases in drought and flood frequency; impacts expected to be greater at lower latitudes and for subsistence farmers
  • regional changes in distribution and population of fish species; adverse effects for aquaculture and fisheries
  • gradual replacement of eastern Amazon tropical forest by savanna due to increased temperatures and decreased soil moisture and associated biodiversity loss
  • increased forest growth in much of Northern Europe, loss in somre regions due to thawing permafrost
  • decreased forest productivity in Central and Eastern Europe
  • decreased crop productivity in Southern Europe due to water stress
  • 5 to 20% increased productivity in rain-fed agriculture in North America with significant variability; crops near warm end of suitability negatively impacted
  • pest, disease, and fire threats to North American forests increase

industry, settlement, & society

  • most vulerable: coastal and river flood plain societies and infrastructure; economies closely linked to climate-sensitive resources; areas prone to extreme weather events
  • poor communities are relatively vulnerable because they lack adaptive capacity and tend to be relatively dependent on climate-sensitive resources (subsistence)
  • major health threats: malnutrition; heat-related; floods; droughts; water-borne disease & associated disease vectors
  • lower winter heating costs in northern Europe!
  • navigable Arctic Ocean!
  • cities that currently experience heat waves will experience more, and more intense heat events
  • Africa is one of the most vulnerable continents due multiple stresses and relatively low adaptive capacity
  • small island nations are especially vulnerable; sea level rise, fisheries, reduced freshwater resources


  • amplified by multiple large stresses and non-climate stresses
  • depends on development pathway (technology, population growth, income growth)
  • sustainable development can reduce vulnerability
  • atmospheric CO2 mitigation can help; many technologies already exist
  • while impacts of climate change vary regionally, in the aggregate it will impose net annual costs that increase over time

A few related links:

The Stern Review of the economics of climate change, commissioned by the UK Chancellor of the Exchequer, concludes that the benefits of strong, early action outweigh the costs (executive summary).

Barbara Boxer's (chair, Senate Environment & Public Works Committee) statement on the AR4 WGII summary.

Flooding impacts in Bhutan.

Christina Hulbe :: 10:00 AM :: Comments (10) :: Digg It!