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Future projections by the Intergovernmental Panel on Climate Change

According to a report by the UN’s Intergovernmental Panel on Climate Change(IPCC), 30% of animal and plant species will be vulnerable to extinction if global temperatures rose by 1.5 to 2.5 degrees Celsius. It says the world’s have-nots would be worst hit by climate change, predicting greenhouse gases would change rainfall patterns, intensify tropical storms, accelerate the melting of Arctic ice and mountain glaciers, and amplify the risk of drought, flooding and water stress.

IPCC holds that Asia faces a heightened risk of flooding, severe water shortages, infectious disease and hunger from global warming this century. The region is confronted by a 90% likelihood that more than a billion of its people will be “adversely affected” by the impacts of global warming by the 2050s.

Its estimates say the magnitude of climate-change effects will vary according to the size of the world’s population, energy use and the level of greenhouse gases in the atmosphere. But under any scenario, the world’s most populous region will be badly hit.

Statements on Global Warming by IPCC ( New York Times)

IPCC notes that using the term “very likely” indicates a likelihood of more than 90%. This is how the the statements about the evidence have evolved and become stronger.

1990 “The unequivocal detection of the enhanced greenhouse effect from observations is not likely for a decade or more”
1995 “The balance of evidence suggests a discernable human influence on global climate”
2001 “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.”
2007 “Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations”.

Sector-wise findings from the 4th Assessment Report regarding projected impacts as well as vulnerability and adaptation

Growing water demand and climate change

120 million to 1.2 billion people in Asia will experience increased water stress by 2020 and 185 to 981 million by 2050.
Per capita water availability in India will drop from around 1900 cubic metre currently to 1,000 cu-metres by 2025.
By mid-century, annual average river runoff and water availability are projected to increase by 10-40% at high latitudes and in some wet tropical areas, and decrease by 10-30% over some dry regions at mid-latitudes and in the dry tropics, some of which are presently water stressed areas.
In the course of the century, water supplies stored in glaciers and snow cover are projected to decline, reducing water availability in regions supplied by meltwater from major mountain ranges, where more than one-sixth of the world population currently lives. Adaptation procedures and risk management practices for the water sector are being developed in some countries and regions that have recognized projected hydrological changes with related uncertainities.

Vulnerability of Indian agriculture to climate change

Cereal yields in South Asia could drop in some areas by up to 30% by 2050.
Crop productivity is projected to increase slightly at mid-to high latitudes for local mean temperature increases of up to 1-3 degrees Celcius depending on the crop, and then decrease beyond that in some regions.
At lower latitudes, especially seasonally dry and tropical regions, crop productivity is projected to decrease for even small local temperature increases (1-2 degrees Celsius), which would increase risk of hunger.
Globally, the potential for food production is projected to increase with increases in local average temperature over a range of 1-3 degrees Celsius, but above this it is projected to decrease.
Increases in the frequency of droughts and floods are projected to affect local crop production negatively, especially in subsistence sectors at low latitudes.

Coastal hazards due to climate change

Even modest rises in sea levels will cause flooding and economic disruption in densly-populated mega-deltas, such as the mouths of the Yangtze in China, the Red River in China and Vietnam, and the Ganges-Brahmaputra delta in low-lying Bangladesh.
Coasts are projected to be exposed to increasing risks, including coastal erosion, due to climate change and sea-level rise. The effect will be exacerbated by increasing human-induced pressures on coastal areas.
Many millions more people are projected to be flooded every year due to sea level rise by the 2080s. Those densly populated and low-lying areas where adaptive capacity is relatively low, and which already face other challenges such as tropical storms or local coastal subsidence, are especially at risk. The numbers affected will be largest in the mega-deltas of Asia and Africa while small islands are especially vulnerable.
Adaptation for coasts will be more challenging in developing countries than in developed countries, due to constraints on adaptive capacity.
The most vulnerable industries, settlements and societies are generally those in coastal and river flood plains, those whose economies are closely linked with climate-sensitive resources, and those in areas prone to extreme weather events, especially where rapid urbanization is occurring. Poor communities can be especially vulnerable, in particular those concentrated in high-risk areas. They tend to have more limited adaptive capacities, and are more dependent on climate-sensitive resources such as local water and food supplies.

Interlinkages with health

Projected climate change-related exposures are likely to affect the health status of millions of people, particularly those with low adaptive capacity, through
a. increases in malnutrition and consequent disorders, with implications for child growth and development;
b. increased deaths, disease and injury due to heat waves, floods, storms, fires and droughts;
c. the increased burden of diarrhoeal disease;
d. the increased frequency of cardio-respiratory diseases due to higher concentrations of ground level ozone related to climate change; and,
e. the altered spatial distribution of some infectious disease vectors.
Cholera and malaria could increase due to flooding and a wider habitat range for mosquitoes.
Climate change is expected to have some mixed effects, such as the decrease or increase of the range and transmission potential of malaria in Africa.
Studies in temperate areas(mainly in industrialized countries) have shown that climate change is projected to bring some benefits, such as fewer deaths from cold exposure. Overall it is expected that these benefits will be outweighed by the negative health effects of rising temperatures world-wide, especially in developing countries.

Impact on ecosystem structure and function

The resilience of many ecosystems is likely to be exceeded this century by an unprecedented combination of climate change, associated disturbances (e.g., flooding, drought, wildfire, insects, ocean acidification), and other global drivers(e.g., land use change, pollution, over-exploitation of resources).
Some 30 per cent of Asian coral reefs, which sustain a large percentage of marine life, are expected to be lost in the next 30 years, although this will occur as a result of multiple stresses.
Over the course of this century, net carbon uptake by terrestrial ecosystems is likely to peak before mid-century and then weaken or even reverse, thus amplifying climate change.
Approximately 20-30% of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5-2.5 degrees Celsius.
The progressive acidification of oceans due to increasing atmospheric carbon dioxide is expected to have negative impacts on marine shell forming organisms (e.g.,corals) and their dependent species.
Regional changes in the distribution and production of particular fish species are expected due to continued warming, with adverse effects projected for aquaculture and fisheries.
Corals are vulnerable to thermal stress and have low adaptive capacity. Increases in sea surface temperature of about 1-3 degrees Celsius are projected to result in more frequent coral bleaching events and widespread mortality, unless there is thermal adaptation or acclimatization by corals.
Coastal wetlands including salt marshes and mangroves are projected to be negatively affected by sea-level rise especially where they are constrained on their landward side, or starved of sediment.

Extreme events in terms of intensity and frequency

In the Himalayas, glaciers less than four kilometers long will disappear entirely if average global temperatures rise by 3 degrees Celsius. This will initially cause increased flooding and mudslides followed by an eventual decrease in flow in rivers that are glacier-fed.
Drought-affected areas will likely increase in extent. Heavy precipitation events, which are very likely to increase in frequency, will augment flood risk.

While extreme weather events become more intense and more frequent, the economic and social costs of those events will increase, and these increases will be substantial in the areas most directly affected. Climate change impacts spread from directly impacted areas and sectors to other areas and sectors through extensive and complex linkages.

 

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