Myles and Wally explain how other factors in the climate system, such as dust particles, water vapour and clouds, can modify the effect on climate of rising levels of greenhouse gases - either decreasing or increasing the temperature rise. A consequence of this is that as dirty emissions from coal-fired power stations are cleaned up, the true greenhouse warming from our CO2 emissions is being unmasked.
Matt, Myles, and Tim paint a picture of our future, in the next 100 years or so, if we make no effort to reduce our greenhouse gas emissions - the 'business as usual' scenario.
The Sami people of Finnmark have traditionally lived close to the land. They have noticed systematic changes in the climate over their lifetimes. Tom Frode, a Norwegian dog-sledder, interprets in English some of their observations.
Katja Riedel and Martin Manning talk about how the levels of CO2 and oxygen in the atmosphere are routinely measured at the Baring Head clean air monitoring station in New Zealand. CO2 is rising and O2 falling.
UN negotiators struggle to seek a global agreement for reducing global CO2 emissions to stabilise the atmospheric CO2 level and keep the global average temperature rise below 2°C. Climate scientists explain why this is important.
Myles Allen explains how the absorption of infrared radiation by the Earth and its atmosphere warms the Earth, and hence how rising CO2 levels increase average global temperature.
Hugh Mortimer and Neil Bowles explain how the absorption of heat by greenhouse gases such as CO2 and water can be measured with a spectrometer.
Ray Pierrehumbert explains in terms of the physics of what happens high up in the atmosphere, how rising levels of greenhouse gases such as carbon dioxide result in warming of the Earth's surface.
It is measured daily around the world, but as Myles notes it's the long term temperature trends that are important. Phil discusses the historical record from weather stations world-wide, and proxy records going back thousands of years