Recent observations show that greenhouse gas emissions and
many
aspects of the climate are changing near the upper boundary of the IPCC
range of projections. Many key climate indicators are already moving
beyond the patterns of natural variability within which contemporary
society and economy have developed and thrived
These indicators include global mean surface temperature, sea-level rise, global ocean emperature, Arctic sea ice extent, ocean acidification, and extreme
climatic events. With unabated emissions, many trends in climate will
likely accelerate, leading to an increasing risk of abrupt or irreversible
climatic shifts.