During the past few decades, two important factors regarding the relationship between humans and the Earth's climate have become apparent. These changes in greenhouse gases and aerosols, taken together, are projected to change regional and global climate and climate-related parameters such as temperature, precipitation, soil moisture, and sea level. Second, some human communities have become more vulnerable to hazards such as storms, floods and droughts as a result of increasing population density in sensitive areas such as river basins and coastal plains. Given current trends of increasing emissions of most greenhouse gases, atmospheric concentrations of these gases will increase through the next century and beyond. With the growth in atmospheric concentrations of greenhouse gases, interference with the climate system will grow in magnitude and the likelihood of adverse impacts from climate change that could be judged dangerous will become greater.
Equity is an important element for legitimizing decisions and promoting cooperation.
An increase of greenhouse gas concentrations leads on average to an additional warming of the atmosphere and the Earth's surface. There are inadequate data to determine whether consistent global changes in climate variability or weather extremes have occurred over the 20th century. This implies that systems typically are more vulnerable in developing countries where economic and institutional circumstances are less favorable. There will likely be reductions in biological diversity and in the goods and services that ecosystems provide society. Some ecological systems may not reach a new equilibrium for several centuries after the climate achieves a new balance.