Observations in the Ocean

Abstract

Evidence of climatic conditions in the distant past has established a link between rising atmospheric CO2 levels and rising global temperatures. Such evidence is for instance obtained from ice cores extracted from polar ice caps or glaciers that formed from the gradual buildup of snow throughout the years. Over the last two centuries, the world’s global mean temperature has increased by 0.6°C (1°F) and it seems that the current trend goes beyond the natural climate variability. In the Arctic, average temperatures have risen almost twice as fast as in the rest of the world and climate changes are being felt particularly intensely. This warming is attributed in good part to human activities. Indeed, the amount of carbon dioxide (CO2) in the atmosphere has increased by 35% since the industrial revolution, mostly due to human activities such as the burning of fossil fuels and the clearing of land. Continuing greenhouse gas releases are projected to cause significant changes in climatic conditions: an increase of 1.4 to 5.8°C (2.5-10.4°F) in global average temperature between 2000 and 2100, as well as changes in ocean currents, sea level and in the amount and distribution of precipitation. Such changes would have significant impacts on human communities as well as ecosystems. About 80% of the world’s growing energy demand is met by burning fossil fuels, which causes a long-lasting increase of CO2 levels in the atmosphere. Therefore, altering the warming trend will be a slow process, even if concerted efforts to reduce emissions are made today.