The concentration of greenhouse gases in the atmosphere presently is equivalent to around 430 parts per million (ppm) CO2 compared with only 280ppm at the beginning of Industrial age and even if the rate of annual accretion to it remain at its current levels the concentration would reach 550ppm carbon dioxide equivalent (CO2) by 2050, or possibly even by 2035.
At 550 ppm CO2e levels, global average temperature rise could exceed 2°C.If no steps are taken to reduce the emissions of greenhouse gases and business continues as usual then the concentration of greenhouse gases could more than treble by the end of the century and at these concentrations there would be 50% risk of global average temperatures increasing by as much as 5°C which is the difference in global surface average temperature between the last ice age and now.
The likely effects of warming under such a scenario would be as follows
- As the earth warms the melting glaciers will initially increase flood risk and then strongly reduce water supplies.
- The declining crop yields on account of less water availability could worsen famine conditions in countries already suffering from food scarcity, especially in Africa .
- While there could be some relief in cold-related deaths but there would be worldwide increase in deaths from malnutrition and heat stress. Vector-borne diseases such as malaria could become more widespread.
- Rising sea levels will result in sea water inundation over habitations of tens to hundreds of millions people in low lying zones with warming of 3 or 4°C. The fresh water availability in coastal areas and low lying islands would decrease significantly.
- Ecosystems will be particularly vulnerable to climate change and around 15-40% of species would potentially face extinction at 2°C of warming.
- Increased absorption of CO2 in the ocean waters would lead to higher levels of ocean acidification that will have major effects on marine ecosystems with adverse consequences on fish stocks.
Stabilization of greenhouse-gas concentrations in the atmosphere is feasible and consistent with continued growth. The benefits of strong, early action outweigh the costs. The annual costs of stabilization at 500-550ppm CO2e would be around one percent of GDP by 2050 but the losses due to delays in taking action could reduce the global GDP by as much as 20%.
Efforts at mitigation have to be global and the following elements are crucial to the success of a global policy for mitigation
- There has to be a cost attached to greenhouse-gas emissions so that individuals and businesses are motivated to switch away from high-carbon goods and services, and to invest in low-carbon alternatives.
- Appropriate technology polices and research funding support is required for the development of a range of low-carbon and high-efficiency technologies.
- Stern Review Report
- At a glance: The Stern Review (Courtesy: BBC website).
For the complete Stern Review Report, click on