Zeev's Turnips Talk Politics (ZTTP)

[Chris McConnel]

From the Union of Concerned Scientists


Are humans contributing to global warming?

In 1995, the world's climate experts in the IPCC concluded for the first time in a cautious consensus, "The balance of evidence suggests that there is a discernible human influence on the global climate."

In its 2001 assessment, the IPCC strengthened that conclusion considerably, saying, "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities."

Scientists have found significant evidence that leads to this conclusion:

     • The observed warming over the past 100 years is  
        unlikely to be due to natural causes alone; it  
        was unusual even in the context of the last  
        1,000 years. 
 

     • There are better techniques to detect climatic  
        changes and attribute them to different causes. 
 

     • Simulations of the climate's response to  
        natural causes (sun, volcanoes, etc.) over the  
        latter half of the 20th century alone cannot  
        explain the observed trends. 
 

     • Most simulation models that take into account  
        greenhouse gas emissions and sulphate aerosols  
        (which have a cooling effect) are consistent  
        with observations over the last 50 years. 

http://www.ucsusa.org/global_environment/global_warming/page.cfm?pageID=497