Climate Change 2001: Synthesis Report

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Figure 3-4: The level of the sea at the shoreline is determined by many factors in the global environment that operate on a great range of time scales, from hours (tidal) to millions of years (ocean basin changes due to tectonics and sedimentation). On the time scale of decades to centuries, some of the largest influences on the average levels of the sea are linked to climate and climate change processes.

Human Health

3.17 Overall climate change is projected to increase threats to human health, particularly in lower income populations predominantly within tropical/ subtropical countries. Climate change can affect human health through multiple pathways, including direct effects (e.g., reduced cold stress in temperate countries but increased heat stress, loss of life in floods and storms) and indirect effects that operate through changes in the ranges of disease vectors (e.g., mosquitoes)5 , water-borne pathogens, water quality, air quality, food availability and quality (e.g., decreased protein content in some cereals), population displacement, and economic disruption (medium to high confidence). Some effects may be beneficial (e.g., reduced cold stress, and reduced disease transmission in some cases), but the predominant effect is anticipated to be adverse (see Table 3-1). Actual impacts will be strongly influenced by local environmental conditions and socio-economic circumstances, and for each anticipated adverse health impact there is a range of social, institutional, technological, and behavioral adaptation options to lessen that impact. Adaptations could, for example, encompass strengthening of the public health infrastructure, health-oriented management of the environment (including air and water quality, food safety, urban and housing design, and surface water management), and the provision of appropriate medical care.

WGII TAR Sections 5.3, 9.1, 9.5, & 9.11

Biodiversity and Productivity of Ecological Systems

3.18 Diversity in ecological systems is expected to be affected by climate change and sea-level rise, with an increased risk of extinction of some vulnerable species (high confidence). Significant disruptions of ecosystems from disturbances such as fire, drought, pest infestation, invasion of species, storms, and coral bleaching events are expected to increase (see Table 3-2). The stresses caused by climate change, added to other stresses on ecological systems (e.g., land conversion, land degradation, harvesting, and pollution), threaten substantial damage to or complete loss of some unique ecosystems, and extinction of some critically endangered and endangered species. Coral reefs and atolls, mangroves, boreal and tropical forests, polar and alpine ecosystems, prairie wetlands, and remnant native grasslands are examples of systems threatened by climate change. In some cases the threatened ecosystems are those that could mitigate against some climate change impacts (e.g., coastal systems that buffer the impacts of storms). Possible adaptation methods to reduce the loss of biodiversity include the establishment of refuges, parks and reserves with corridors to allow migration of species, and the use of captive breeding and translocation of species.

WGII TAR Sections 5.2.3, 5.4.1, 16.2, 17.2, & 19.3.2-3
Table 3-1: Human health consequences of climate change if no climate policy interventions are made.
  2025 2050 2100
CO2 concentrationa 
405-460 ppm 445-640 ppm 540-970 ppm
Global mean temperature change from the year 1990b 0.4-1.1°C 0.8-2.6°C 1.4-5.8°C
Global mean sea-level rise from the year 1990b 3-14 cm 5-32 cm 9-88 cm
Human Health Effectsc
Heat stress and winter mortality [WGII TAR Section 9.4] Increase in heat-related deaths and illness (high confidenced).
Decrease in winter deaths in some temperate regions (high confidenced).
Thermal stress effects
amplified (high confidenced).
Thermal stress effects amplified (high confidenced).
Vector- and water-borne diseases [WGII TAR Section 9.7]   Expansion of areas of potential transmission of malaria and dengue (medium to high confidenced). Further expansion of areas of potential transmission (medium to high confidenced).
Floods and storms [WGII TAR Sections 3.8.5 & 9.5] Increase in deaths, injuries, and infections associated with extreme weather (medium confidenced). Greater increases in deaths, injuries, and infections (medium confidenced). Greater increases in deaths, injuries, and infections (medium confidenced).
Nutrition [WGII TAR Sections 5.3.6 & 9.9]
Poor are vulnerable to increased risk of hunger, but state of science very incomplete. Poor remain vulnerable to increased risk of hunger. Poor remain vulnerable to increased risk of hunger.
a. The reported ranges for CO2 concentration are estimated with fast carbon cycle models for the six illustrative SRES scenarios and correspond to the minimum and maximum values estimated with a fast carbon cycle model for the 35 SRES projections of greenhouse gas emissions. See WGI TAR Section 3.7.3.
b. The reported ranges for global mean temperature change and global mean sea-level rise correspond to the minimum and maximum values estimated with a simple climate model for the 35 SRES projections of greenhouse gas and SO2 emissions. See WGI TAR Sections 9.3.3 and 11.5.1.
c. Summary statements about effects of climate change in the years 2025, 2050, and 2100 are inferred from Working Group II's assessment of studies that investigate the impacts of scenarios other than the SRES projections, as studies that use the SRES projections have not been published yet. Estimates of the impacts of climate change vary by region and are highly sensitive to estimates of regional and seasonal patterns of temperature and precipitation changes, changes in the frequencies or intensities of climate extremes, and rates of change. Estimates of impacts are also highly sensitive to assumptions about characteristics of future societies and the extent and effectiveness of future adaptations to climate change. In consequence, summary statements about the impacts of climate change in the years 2025, 2050, and 2100 must necessarily be general and qualitative. The statements in the table are considered to be valid for a broad range of scenarios. Note, however, that few studies have investigated the effects of climate changes that would accompany global temperature increases near the upper end of the range reported for the year 2100.
d. Judgments of confidence use the following scale: very high (95% or greater), high (67-95%), medium (33-67%), low (5-33%), and very low (5% or less). See WGII TAR Box 1-1.

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