**3.2.9 Aggregate economic impacts of climate change**

186 Fossil Fuel and the Environment

respiratory diseases, and with premature mortality.

than increases in heat-related deaths in the UK.

**3.2.7 Water resources crisis** 

high confidence, that:

chemical reactions involving nitrogen oxides and other compounds. The reaction is a photochemical reaction, meaning that it involves electromagnetic radiation, and occurs in the presence of bright sunshine and high temperatures. Exposure to elevated concentrations of ozone is associated with increased hospital admissions for pneumonia, chronic obstructive pulmonary disease, asthma, allergic rhinitis and other

Background levels of ground-level ozone have risen since pre-industrial times because of increasing emissions of methane, carbon monoxide and nitrogen oxides (*Confalonieri* 

 *Cold-waves*: Cold-waves continue to be a problem in northern latitudes, where very low temperatures can be reached in a few hours and extend over long periods (*Confalonieri et al., 2007l*). Reductions in cold-deaths due to climate change are projected to be greater

A number of climate-related trends have been observed that affect water resources. These include changes in precipitation, the crysosphere and surface waters (e.g., changes in river flows). Observed and projected impacts of climate change on freshwater systems and their management are mainly due to changes in temperature, sea level and precipitation variability. Sea level rise will extend areas of salinization of groundwater and estuaries, resulting in a decrease in freshwater availability for humans and ecosystems in coastal areas. In an assessment of the scientific literature, *Kundzewicz et al. (2007)* concluded, with

 The negative impacts of climate change on freshwater systems outweigh the benefits. All of the regions assessed in the IPCC Fourth Assessment Report (Africa, Asia, Australia and New Zealand, Europe, Latin America, North America, Polar regions (Arctic and Antarctic), and small islands) showed an overall net negative impact of

 Semi-arid and arid areas are particularly exposed to the impacts of climate change on freshwater. It has been assessed that many of these areas, e.g., the Mediterranean basin, Western United States, Southern Africa, and north-eastern Brazil, would suffer a

General circulation models project that the future climate change will bring wetter coasts, drier mid-continent areas, and further sea level rise (*Scott, MJ, et.al., 1996*). Such changes could result in the gravest effects of climate change through sudden human migration. Millions might be

Migration related to climate change is likely to be predominantly from rural areas in developing countries to towns and cities. In the short term climate stress is likely to add incrementally to existing migration patterns rather than generating entirely new flows of people. It is quite likely that environmental degradation, loss of access to resources (e.g., water resources) (*Desanker, P., et al., 2001*) and resulting human migration could become a source of political and even military conflict. Factors other than climate change may, however, be more

climate change on water resources and freshwater ecosystems.

displaced by shoreline erosions, river and coastal flooding, or severe drought.

decrease in water resources due to climate change.

**3.2.8 Environmental migration and conflict** 

*et al., 2007k*). This trend is expected to continue into the mid-21st century.

Aggregating impacts adds up the total impact of climate change across sectors and/or regions. Examples of aggregate measures include economic cost (e.g., changes in gross domestic product (GDP) and the social cost of carbon), changes in ecosystems (e.g., changes over land area from one type of vegetation to another), human health impacts, and the number of people affected by climate change (*Smith, J.B., et al., 2001*).

Economic impacts are expected to vary regionally. For a medium increase in global mean temperature (2-3 °C of warming, relative to the average temperature between 1990-2000), market sectors in low-latitude and less-developed areas might experience net costs due to climate change. On the other hand, market sectors in high-latitude and developed regions might experience net benefits for this level of warming. A global mean temperature increase above about 2-3 °C (relative to 1990-2000) would very likely result in market sectors across all regions experiencing either declines in net benefits or rises in net costs.

Aggregate impacts have also been quantified in non-economic terms. For example, climate change over the 21st century is likely to adversely affect hundreds of millions of people through increased coastal flooding, reductions in water supplies, increased malnutrition and increased health impacts.
