Understanding past climate changes can be key to understanding the state of the climate in the future. On May 9, 2013, carbon dioxide levels in the atmosphere reached the level of 400 parts per million (ppm). The last time the Earth experienced this level of carbon dioxide was in the Pliocene about three to five million years ago.
In the mid-Pliocene average global temperatures were 2-3 deg C higher than today, and sea levels were 25 to 30 metres higher than today.Cooling and drying occurred in the late Pliocene. These changes were likely caused by reducing levels of CO2 in the atmosphere due to increased chemical weathering (many mountain ranges uplifted in this period), increasing ice at high latitudes giving increased albedo, and possibly reduced solar insolation.
The data on CO2 concentrations demonstrate a clear correspondence between the Pliocene climate (due to natural causes) and the contemporary climate conditions (caused by anthropogenic actions). What really worries scientists about our contemporary CO2 concentrations is the breakneck speed at which they are increasing.
No comments:
Post a Comment