The Development of Climate Change
1. How and why has climate changed in the past?
Our climate has changed a lot over the past 2 billion years, Earth’s climate has alternated from “Ice House” like today’s climate and “Hot House” like the dinosaur period.
The average temperature on planet Earth has risen by 1.1 degrees F since the beginning of the 20th century, most of the warming in the 20th century happened from about 1910 to 1945 and since 1976.
20th century warming is likely to be the biggest, during any century over the past 1,000 years for the Northern Hemisphere.
There has been a large retreat of mountain glaciers in non-polar regions during the 20th century. Northern hemisphere sea-ice extent has decreased 10% since the 1950s, and Arctic summer sea/ice thickness is likely to have decreased by 40%.
Sea level has risen between 10 - 25 cm largely due to warmth expansion of the oceans and to a lesser extent due to the melting of land based Ice Mountains. The rate of sea level rise during the 20th century was about 10 times higher than the average rate during the last 3,000 years. Global ocean heat content has also increased since the 1950s.
Definition – a warm ocean current of variable intensity that develops after late December along the coast of Ecuador and Peru and sometimes causes catastrophic weather conditions.
More frequent, determined and fierce El Nino’s have been recorded in recent decades. The constant 1990 to mid-1995 warm phase of the El Nino Southern Oscillation event was amazing in the 120 year record of the rare occasion. The 1997 El Nino event appears to have been the strongest on record. Whilst scientists cannot yet say with certainty that this observed change is due to human activity, this observation is regular with some climate model predictions. With climate change, they suggest a warming pattern in the Pacific ocean similar to what occurs during an El Nino event now. Against this background warming,...