A recent IPCC report (Summary for Policy Makers) has stated, without reservation, "Warming of the climate is unequivocal." This same report states that 11 of last 12 years were the hottest ever recorded (since 1850).
Furthermore, the report states that the high temperatures of the last 50 years are unusual for at least the last 1300 years. A number of plots of the avearge global surface temperature vs. time have been developed to cover the period prior to instrumented records. These plots typically include inferred temperatures using various techniques (e.g., tree ring or ice core data) by different researchers. A plot of this type by Jones and Mann clearly demonstrtes the rapid increase in global surface temperature over the last 150 years.
There is general consensus among scientific bodies on the reality and seriousness of global warming issue:
• National Science Academies Joint Statement (US, UK, Russia, Japan, etc.)
• Kyoto Protocol
• 928 Peer reviewed scientific papers
• Arctic Climate Impact Assessment
• Our Changing Planet, US Climate Change Science Program Report
• IPCC
• National Academy of Sciences
• United Nations Framework Convention on Climate Change
