1. Observed changes in climate and their effects
- Warming of the climate system is unequivocal, as is now evident from increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level.
2. Causes of change
- Global GHG emissions due to human activities have grown since pre-industrial times, with an increase of 70 % between 1970 and 2004.
- Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations.
3. Projected climate change and its impacts
- Continued GHG emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century.
- Anthropogenic warming could lead to some impacts that are abrupt or irreversible, depending upon the rate and magnitude of the climate change.
4. Adaptation and mitigation options
- A wide array of adaptation options is available, but more extensive adaptation than is currently occurring is required to reduce vulnerability to climate change.
- Governments can put into action a wide array of policies and measures to stimulate mitigation.
- Notable achievements of the UNFCCC and its Kyoto Protocol are the establishment of a global response to climate change, stimulation of an array of national policies, and the creation of an international carbon market and new institutional mechanisms that may provide the foundation for new mitigation efforts.
5. The long-term perspective
- Neither adaptation nor mitigation alone can avoid all climate change impacts ; however they can complement each other and together can significantly reduce the risks of climate change.
- All stabilization levels assessed can be achieved by deployment of a portfolio of technologies that are either currently available or expected to be commercialized in coming decades, assuming appropriate and effective incentives are in place for their development, acquisition, deployment and diffusion and addressing related barriers.
Note: there is an attenuation of the controversy aroused by the findings of the IPCC on their publication. However, some schools of scientific thought, without denying the reality of anthropogenic climate change, continue to downplay its importance.
Source: IPCC, Climate Change 2007: Assessment Report, Summary for Policymakers (2007).