Read what John Houghton, the former head of the UK Meteorological Office, had to say (2003/07/29)
 And (this should scare you, if nothing else does) read what the US Department of Defense thinks about global warming (Observer 2004/02/22)

  This informative graph obtained from http://www.met-office.gov.uk/research/hadleycentre/CR_data/Annual/HadCRUG.gif
That website has recently completely changed and this particular file is no longer available, but the same underlying data and a straightforward explanation of the current (Jan 2011) Hadley Center/UK Met Office global temperature record is here:
http://www.metoffice.gov.uk/climate-change/guide/science/explained/temp-records
Or the updated record to 2010 with explanation is here: http://www.cru.uea.ac.uk/cru/info/warming/

Because adequate global temperature records from thermometers are not available before 1850, all information on global climate before this time comes from geological ("proxy") records, including ice cores, coral and tree ring records, and stratified sedimentary deposits. Geological scientists have provided evidence of fundamental and primary importance both in setting the longer-term context of warming given by the thermometer temperature record, and of the potential consequences, from previous geological events of major climate change due to carbon release to the atmosphere. The ice core record  The millenial proxy temperature record  Paleocene-Eocene thermal maximum event

The American Geophysical Union's position statement on Human impacts on Climate
The Geological Society of America's position statement on Climate Change
The Geological Society of London's position statement on Climate Change: evidence from the geological record

Return to Planet of the aliens
or to The significance of Geology
or, if you refuse to take seriously the evidence for global warming/climate change, and the (potentially catastrophic) consequences,
uageo.www.expressspacetransit offers you the alternative of a free one-way (non-refundable) ticket to Alpha Centauri.......