Trends in global climate change

Temperature changes 

Recent studies indicated the evidence of climate change. A range of climate indicators show that the twentieth century is warmer than any other century. Global mean surface temperatures have risen by 0.74oc ± 0.18oc over the last 50 years than over the 100 years. The instrumental record of global surface temperature recorded 1998 and 2005 as warmest years. Mean surface temperatures increasing markedly from 1900 by 1.2 – 1.4 ^oF. During this period there was a rapid temperature increase in 1910-1930 and 1970’s. There have been observed spatial variations in temperature. For example, greater warming observed over mid latitude continental areas during winter and spring. 

Lower – tropospheric temperatures showed slightly greater warming rates over the period 1958 to 2005. Lower stratospheric temperatures are cooling since 1979. Tropospheric water vapour is increasing after 1976’^s by higher temperatures over both land and ocean. 

Droughts have become common in tropics and sub tropics since the 1970. Declined land precipitation and increased temperatures are enhancing the evapotranspiration and drying. The regions where droughts have occurred determined by the changes of sea surface temperature. These changes associated through atmospheric circulation and precipitation. Australia and Europe recent droughts events are accompanying with the extreme nature of high temperatures and heat waves. Temperature increases accelerated the wildfire. Worst wildfire occurred in April 2009 at Southern California. It destroyed 8,100 hectares land area.

Changes in precipitation 

Precipitation has shown increased trend over land north of 30⁰ N over the period 1900 to 2005. In tropics downward trends dominate since the 1970’s. Tropical values become significantly wetter in eastern parts of North and South America, Northern Europe, and Northern and central Asia. Drier in the Sahel, the Mediterranean, Southern Africa and parts of Southern Asia.

Records of land surface precipitation show increase trend over much of the Northern hemisphere’s mid and high latitudes by 0.5 to 1percent per decade. In Sub-tropical land areas, precipitation has slightly declined by 0.3% per decade. There is also evidence of precipitation increases over the tropical oceans and tropical land areas. In Vietnam heavy rain and floods occurred in October 2008. The frequency and intensity of precipitation also varied over the annual, decadal and multi-decadal time scales. 

Oceanic climate change & sea level rise 

The rise in global mean sea level is another indicator of global warming. This warming events result from thermal expansion of the oceans and the melting of glaciers and ice sheets. The Tide gauge measurements suggest that sea level has risen worldwide approximately 6-8 inches during last century. During the period of 1961-2003 mean sea level raised by 1.8 ± 0.55 mm. 

According to the National Aeronautics and space Administration’s (NASA) Earth observatory, satellite measurements estimate that sea level has been rising at a rate of 9 to 13 inches per century since 1993. 

Intense tropical cyclone activity has increased since about 1970. Sea surface temperature and other critical variables have influence on tropical thunder storm and tropical storm development. For example, the Atlantic basin was extremely active with number of tropical storms system including hurricanes between the periods of 1995-2005. Recently strongest tropical cyclone occurred in Madagascar in February 2008. 

Changes in Snow

The cryosphere have complex linked with the surface energy budget, the water cycle, sea level change and the surface gas exchange. Recent decreases in ice mass are related with rising surface air temperatures. Especially this changes observed in north of 65⁰N. 

The volumes of Green land, Antarctica, Artic and Himalaya Ice sheets are start to melt rapidly. According to Artic researches ice sheet has been 2m thicker and shrink as 42% and that region lost 6% glacier ice sheet. Temperature increase 3⁰C over western part of the Antarctica over the past 50 years. Alaska lost 500 cubic mile of glaciers over the past 50 years. 

The cryosphere on land stores about 75% of the world’s fresh water. Changes in ice mass have contributes recent sea level changes and affect the fresh water availability in many mountains and surrounding regions. The high albedo of snow has an important influence on the surface energy budget and on earth’s radiative balance (e.g., Groisman et al, 1994). 

 References :

(1) Kevin T. Pickering an Lewis A.Owen (1997); An introduction to global environmental issues; London and New york 

(2) Catrinus J. Jepma and Mohan Munasinghe (1998); Climate change policy (facts, issues, and analyses); Cambridge university press.

(3) http://www.unep.org/pdf/ccScienceCompendium2009/cc_ScienceCompendium2009_ch1_en.pdf

(4) http://www.arctic.noaa.gov/reportcard/sea_ice_ocean.html