TABLE 5-2 Climate-Related Observed Trends of Various Components of the Global Freshwater Systems

 

Observed Climate-Related Trends

Precipitation

Increasing over land north of 30°N over the period of 1901-2005

Decreasing over land between 10°S and 30°N after the 1970s (WGI AR4, Chapter 3, Executive Summary)

Increasing intensity of precipitation (WGI AR4, Chapter 3, Executive Summary)

Cryosphere

 

Snow cover

Decreasing in most regions, especially in spring (WGI AR4, Chapter 4, Executive Summary)

Glaciers

Decreasing almost everywhere (WGI AR4, Chapter 4, Section 4.5)

Permafrost

Thawing between 0.02 m/yr (Alaska) and 0.4 m/yr (Tibetan Plateau) (WGI AR4, Charter 4, Executive Summary; WGII AR4, Chapter 15, Section 15.2)

Surface Waters

 

Streamflow

Increasing in Eurasian Arctic, significant increases or decreases in some river basins (WGII AR4 Chapter 1, Section 1.3.2)

Earlier spring peak flows and increased winter base flows in Northern America and Eurasia (WGII AR4, Chapter 1, Section 1.3.2).

Evapotranspiration

Increased actual evapotranspiration in some areas (WGI AR4, Chapter 3, Section 3.3.3).

Lakes

Warming, significant increases or decreases of some lake levels, and reduction in ice cover (WGII AR4, Chapter 1, Section 1.3.2).

Groundwater

No evidence for ubiquitous climate-related trend (WGII AR4, Chapter 1, Section 1.3.2)

Floods and Droughts

 

Floods

No evidence for climate-related trend (WGII AR4, Chapter 1, Section 1.3.2), but flood damages are increasing (WGII AR4, Chapter 3, Section 3.2)

Droughts

Intensified droughts in some drier regions since the 1970s (WGII AR4, Chapter 1, Section 1.3.2; WGI AR4, Chapter 3, Executive Summary)

Water quality

No evidence for climate-related trend (WGII AR4, Chapter 1, Section 1.3.2)

Erosion and sediment transport

No evidence for climate-related trend (WGII AR4, Chapter 3, Section 3.2)

Irrigation water demand

No evidence for climate-related trend (WGII AR4, Chapter 3, Section 3.2)

NOTES: WGI AR4, Chapter 3, Trenberth et al. 2007; WGI AR4, Chapter 4, Lemke et al. 2007; WGII AR4, Chapter 1, Rosenzweig et al. 2007; WGII AR4, Chapter 3, Kundzewicz et al. 2007; and WGII AR4, Chapter 15, Anisimov et al. 2007.

SOURCE: Kundzewicz et al. 2007, p.177, Table 3.1. Reprinted with permission; copyright 2007, Intergovernmental Panel on Climate Change.



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