by 0.1 to 0.9 metres over the same period. The wide range in projections is based upon several different scenarios that assume different levels of future CO2 emissions (see the section below on Projections in the TAR). Synthesis Report The TAR Synthesis Report includes a summary of the TAR's main findings and uncertainties. "Robust findings" of the TAR include: Observed warming of the Earth's surface, attribution of observed warming to human activities, projected increases in future global mean temperature, rising sea levels, and increased frequency of heat waves. Future warming will have both beneficial and adverse effects, but for higher levels of warming, adverse effects will predominate. Developing countries and poor persons are most vulnerable to climate change. "Key uncertainties" in the TAR include: Estimated climate forcings of natural climatic factors and anthropogenic aerosols (e.g., sulfate, which is produced when sulfur-rich coal is burnt), future changes in greenhouse gas (GHG) emissions, and the role of climate feedbacks, which may amplify or reduce the magnitude of future climate change; Assigning probabilities to projections of changes in sea level and temperature, as well as uncertainties related to regional projections of climate change. Projections Projections are used in the TAR as a guide to the possible future effects of climate change, e.g., changes in global mean temperature and sea level. In the TAR, the word "projection" is favoured over "prediction". This is because many future changes related to climate are highly uncertain. For example, climate change projections are affected by highly uncertain changes in future GHG emissions. The TAR projects impacts according to possible future changes in global mean temperature. Other projections are based on scenarios that the IPCC has developed. In 2000, the IPCC published 40 different scenarios (the "SRES" scenarios) which contain estimates of future changes in anthropogenic emissions of greenhouse gases and aerosols. The SRES scenarios project a wide range of possible changes in future social and economic development, and projected climate change impacts vary according to the scenario considered. The IPCC has not assigned probabilities to the 40 SRES scenarios. Some authors have argued that some SRES scenarios are more likely to occur than others. Scientific opinion The IPCC is backed by the scientific community. For example, a joint statement of support was issued in May 2001 by the science academies of Australia, Belgium, Brazil, Canada, the Caribbean, China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, New Zealand, Sweden