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IPCC Synthesis Report Part II - Habiba Gitay. Climate change: observed and projected–changes in the mean state, variability and extreme events
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IPCC Synthesis ReportPart II - Habiba Gitay • Climate change: observed and projected–changes in the mean state, variability and extreme events • Observed and projected impacts of climate change on ecological systems, socio-economic sectors (including human health), and approaches to adapt to climate change
Human activities have changed the composition of the atmosphere since the pre- industrial era
Atmosphere The KP seeks to reduce total emissions by about 0.2 This is the “greenhouse” problem 3.3 Humans are perturbing the carbon cycle 750 62.3 Estimated Fossil Deposits 6.3 About 16,000 60 1.6 Plants Driven by fossil fuel emissions 500 Soil 90 92.3 2000 …and land clearing Oceans 39,000 UnitsGt C for stores & Gt C y-1 for fluxes The oceans and land vegetation are currently taking up 4.6 Gt C per year
El Niño years La Niña years The frequency, persistence and magnitude of El-Nino events have increased in the last 20 years The El-Nino phenomena leads to floods and droughts throughout the tropics and subtropics
Observed regional changes in temperature have been associated with observed changes in physical and biological systems Examples include: • non-polar glacier retreat • reduction in Arctic sea ice extent and thickness in summer • earlier flowering and longer growing and breeding season for plants and animals in the N.H. • poleward and upward (altitudinal) migration of plants, birds, fish and insects; earlier spring migration and later departure of birds in the N.H. • increased incidence of coral bleaching
Most of the observed warming in the past 50 years is attributable to human activities
Greenhouse gas emissions and concentrations, temperature and sea level are projected to change
Global mean surface temperature is projected to increase during the 21st century
Land areas are projected to warm more than the oceans with the greatest warming at high latitudes Annual mean temperature change, 2071 to 2100 relative to 1990: Global Average in 2085 = 3.1oC
Some areas are projected to become wetter, others drier with an overall increase projected Annual mean precipitation change: 2071 to 2100 Relative to 1990
Mean sea level is projected to rise by 0.09 to 0.88m by 2100, but with significant regional variations
Projected changes during the 21st century Examples of impacts Extreme Weather Events are Projected to Increase • Higher maximum temperatures; more hot days and heatwavesover nearly all land areas (very likely) • Higher minimum temperatures; fewer cold daysfrost days and cold spells over nearly all land areas (very likely) • more intense precipitation events over many areas (very likely) • increased summer drying over most mid-latitude continental interiors and associated risk of drought (likely) • increase in tropical cyclone peak wind intensity, mean and peak precipitation intensities (likely) • Increased mortality in old people in urban areas • Damage to crops • Heat stress on livestock • Extended range of pests and diseases • Loss of some crop/fruit • Land slides, mudslides, damage to property and increased insurance costs • Reduced rangeland productivity, increased wildfires, decreased hydropower • Damage to various ecological and socioeconomic systems
More adverse than beneficial impacts on biological and socioeconomic systems are projected
Increased water availability in some water-scarce regions, and decreased water availability in many water scarce regions
Initially increased agricultural productivity in some mid-latitude regions & reduction in the tropics and sub-tropics even with warming of a few degrees 2020s 2050s 2080s
Significant disruptions of ecosystems from disturbances such as fire, drought, pest infestation and invasion of speciesChanges in the productivity and composition of ecological systems, with coral reefs and boreal forests being most vulnerable
Branching coral Brain coral coral bleaching events are expected to increase
Ecological systems have many interacting non-linear processes and are thus subject to abrupt changes and threshold effects arising from relatively small changes in driving variables, such as climate. For example: Temperature increase beyond a threshold, which varies by crop and variety, can affect key development stages of some crops and result in severe losses in crop yields.
Increased risk of floods, potentially displacing tens of millions of people, due to sea level rise and heavy rainfall events, especially in Small Island States and low-lying deltaic areas. Bangladesh is projected to lose about 17% of its land area with a sea level rise of one meter - very difficult to adapt due to lack of adaptive capacity projected present
Effect on human health…Reduced winter mortality in mid- and high-latitudes Increased incidence of heat stress mortality, and the number of people exposed to vector-borne diseases, such as malaria and dengue and water-borne diseases such as cholera, especially in the tropics and sub-tropics
Developing countries are the most vulnerable to climate change • Impacts are worse - already more flood and drought prone and a large share of the economy is in climate sensitive sectors • Lower capacity to adapt because of a lack of financial, institutional and technological capacity and access to knowledge • Climate change is likely to impact disproportionately upon the poorest countries and the poorest persons within countries, exacerbating inequities in health status and access to adequate food, clean water and other resources. • Net market sector effects are expected to be negative in most developing countries
Adaptation has the potential to reduce adverse effects of climate change and can often produce immediate ancillary benefits, but cannot prevent all damages • Numerous adaptation options have been identified that can reduce adverse and enhance beneficial impacts of climate change, but will incur costs • Greater and more rapid climate change would pose greater challenges for adaptation
