IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability

Executive summary

Climatic variability and extreme events have been severely affecting the Latin America region over recent years (high confidence).

Highly unusual extreme weather events were reported, such as intense Venezuelan rainfall (1999, 2005), flooding in the Argentinean Pampas (2000-2002), Amazon drought (2005), hail storms in Bolivia (2002) and the Great Buenos Aires area (2006), the unprecedented Hurricane Catarina in the South Atlantic (2004) and the record hurricane season of 2005 in the Caribbean Basin [13.2.2]. Historically, climate variability and extremes have had negative impacts on population; increasing mortality and morbidity in affected areas. Recent developments in meteorological forecasting techniques could improve the quality of information necessary for people’s welfare and security. However, the lack of modern observation equipment, the urgent need for upper-air information, the low density of weather stations, the unreliability of their reports and the lack of monitoring of climate variables work together to undermine the quality of forecasts, with adverse effects on the public, lowering their appreciation of applied meteorological services as well as their trust in climate records. These shortcomings also affect hydrometeorological observing services, with a negative impact on the quality of early warnings and alert advisories (medium confidence). [13.2.5]

During the last decades important changes in precipitation and increases in temperature have been observed (high confidence).

Increases in rainfall in south-east Brazil, Paraguay, Uruguay, the Argentinean Pampas and some parts of Bolivia have had impacts on land use and crop yields, and have increased flood frequency and intensity. On the other hand, a declining trend in precipitation has been observed in southern Chile, south-west Argentina, southern Peru and western Central America. Increases in temperature of approximately 1°C in Mesoamerica and South America, and of 0.5°C in Brazil, were observed. As a consequence of temperature increases, the trend in glacier retreat reported in the Third Assessment Report is accelerating (very high confidence). This issue is critical in Bolivia, Peru, Colombia and Ecuador, where water availability has already been compromised either for consumption or for hydropower generation []. These problems with supply are expected to increase in the future, becoming chronic if no appropriate adaptation measures are planned and implemented. Over the next decades Andean inter-tropical glaciers are very likely to disappear, affecting water availability and hydropower generation (high confidence). []

Land-use changes have intensified the use of natural resources and exacerbated many of the processes of land degradation (high confidence).

Almost three-quarters of the drylands are moderately or severely affected by degradation processes. The combined effects of human action and climate change have brought about a continuous decline in natural land cover at very high rates (high confidence). In particular, rates of deforestation of tropical forests have increased during the last 5 years. There is evidence that biomass-burning aerosols may change regional temperature and precipitation in the southern part of Amazonia (medium confidence). Biomass burning also affects regional air quality, with implications for human health. Land-use and climate changes acting synergistically will increase vegetation fire risk substantially (high confidence). [13.2.3,]

The projected mean warming for Latin America to the end of the century, according to different climate models, ranges from 1 to 4°C for the SRES emissions scenario B2 and from 2 to 6°C for scenario A2 (medium confidence).

Most general circulation model (GCM) projections indicate rather larger (positive and negative) rainfall anomalies for the tropical portions of Latin America and smaller ones for extra-tropical South America. In addition, the frequency of occurrence of weather and climate extremes is likely to increase in the future; as is the frequency and intensity of hurricanes in the Caribbean Basin. [,]

Under future climate change, there is a risk of significant species extinctions in many areas of tropical Latin America (high confidence).

Replacement of tropical forest by savannas is expected in eastern Amazonia and the tropical forests of central and southern Mexico, along with replacement of semi-arid vegetation by arid vegetation in parts of north-east Brazil and most of central and northern Mexico due to synergistic effects of both land-use and climate changes (medium confidence) [13.4.1]. By the 2050s, 50% of agricultural lands are very likely to be subjected to desertification and salinisation in some areas (high confidence) [13.4.2]. Seven out of the 25 most critical places with high endemic species concentrations are in Latin America and these areas are undergoing habitat loss. Biological reserves and ecological corridors have been either implemented or planned for the maintenance of biodiversity in natural ecosystems, and these can serve as adaptation measures to help protect ecosystems in the face of climate change. []

By the 2020s, the net increase in the number of people experiencing water stress due to climate change is likely to be between 7 and 77 million (medium confidence).

While, for the second half of the century, the potential water availability reduction and the increasing demand from an increasing regional population would increase these figures to between 60 and 150 million. [13.4.3]

Generalised reductions in rice yields by the 2020s, as well as increases in soybean yields, are possible when CO2 effects are considered (medium confidence).

For other crops (wheat, maize), the projected response to climate change is more erratic, depending on the chosen scenario. If CO2 effects are not considered, the number of additional people at risk of hunger under the A2 scenario is likely to reach 5, 26 and 85 million in 2020, 2050 and 2080, respectively (medium confidence). On the other hand, cattle and dairy productivity is expected to decline in response to increasing temperatures. [13.4.2]

The expected increases in sea-level rise (SLR), weather and climatic variability and extremes are very likely to affect coastal areas (high confidence).

During the last 10-20 years the rate of SLR has increased from 1 to 2-3 mm/yr in south-eastern South America []. In the future, adverse impacts would be observed on: (i) low-lying areas (e.g., in El Salvador, Guyana and the coast of Buenos Aires Province in Argentina), (ii) buildings and tourism (e.g., in Mexico and Uruguay); (iii) coastal morphology (e.g., in Peru); (iv) mangroves (e.g., in Brazil, Ecuador, Colombia and Venezuela); (v) availability of drinking water on the Pacific coast of Costa Rica, Ecuador and the Rio de la Plata estuary. In particular, sea-level rise is very likely to affect both Mesoamerican coral reefs (e.g., in Mexico, Belize and Panama) and the location of fish stocks in the south-east Pacific (e.g., in Peru and Chile). [13.4.4]

Future sustainable development plans should include adaptation strategies to enhance the integration of climate change into development policies (high confidence).

Some countries have made efforts to adapt, particularly through conservation of key ecosystems, early warning systems, risk management in agriculture, strategies for flood, drought and coastal management, and disease surveillance systems. However, the effectiveness of these efforts is outweighed by: a lack of basic information, observation and monitoring systems; lack of capacity-building and appropriate political, institutional and technological frameworks; low income; and settlements in vulnerable areas; among others [13.2]. Without improvements in these areas, the Latin America countries’ sustainable development goals will be seriously compromised, adversely affecting, among other things, their ability to reach the Millennium Development Goals [13.5].