IPCC First Assessment Report 1990 IPCC Second Assessment Report: Climate Change 1995 IPCC Third Assessment Report: Climate Change 2001 IPCC Fourth Assessment Report: Climate Change 2007 IPCC Fifth Assessment Report: Climate Change 2013/14

A total of 209 Lead Authors 50 Review Editors from 39 countries more than 600 Contributing Authors from 32 countries

We are certain of the following: there is a natural greenhouse effect IPCC First Assessment Report 1990 We calculate with confidence that:...CO 2 has been responsible for over half the enhanced greenhouse effect We predict an increase of global mean temperature during the [21st] century of about 0.3 o C per decade (to help you with the Maths, that’s about 3 o C through the century!)

Carbon dioxide remains the most important contributor to climate change; Projections of future global mean temperature change and sea level rise confirm the potential for human activities to alter the Earth's climate to an extent unprecedented in human history; The long time-scales governing both the accumulation of greenhouse gases in the atmosphere and the response of the climate system to those accumulations, means that many important aspects of climate change are effectively irreversible IPCC Second Assessment Report: Climate Change 1995

IPCC Third Assessment Report: Climate Change 2001 An increasing body of observations gives a collective picture of a warming world and other changes in the climate system. Emissions of greenhouse gases and aerosols due to human activities continue to alter the atmosphere in ways that are expected to affect the climate. Confidence in the ability of models to project future climate has increased There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities Human influences will continue to change atmospheric composition throughout the 21st century Global average temperature and sea level are projected to rise under all IPCC scenarios.

Carbon dioxide, methane, and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values The amount of carbon dioxide in the atmosphere in 2005 (379 ppm) exceeds by far the natural range of the last 650,000 years (180 to 300 ppm)ppm Warming in the last 100 years has caused about a 0.74 °C increase in global average temperature. This is up from the 0.6 °C increase in the 100 years prior to the Third Assessment Report. Average Arctic temperatures increased at almost twice the global average rate in the past 100 years. Mountain glaciers and snow cover have declined on average in both hemispheres IPCC Fourth Assessment Report: Climate Change 2007 Changes in the atmosphere

Warming of the atmosphere and ocean system is unequivocal There is a clear human influence on the climate IPCC Fifth Assessment Report: Climate Change 2013/14 It is extremely likely that human influence has been the dominant cause of observed warming since 1950 It is likely (with medium confidence) that 1983—2013 was the warmest 30-year period for 1400 years. It is virtually certain the upper ocean warmed from 1971 to It can be said with high confidence that the Greenland and Antarctic ice sheets have been losing mass in the last two decades. There is high confidence that the sea level rise since the middle of the 19th century has been larger than the mean sea level rise of the prior two millennia. Concentration of greenhouse gases in the atmosphere has increased to levels unprecedented on earth in 800,000 years.