What are the reasons? Radiation balance Energy coming into the Earth from the Sun — SOLAR radiation Energy leaving the Earth to outer Space — INVISIBLE INFRARED radiation INFRARED radiation
Solar radiation at poles and equator Near the poles, the Sun’s rays are spread out over a wide area, so the heating is less intense Near the equator, the Sun’s rays are spread out over a smaller area, so the heating is more intense The Earth’s climate systems in the atmosphere and oceans transport heat between the equator and the poles - and produce the ‘weather’ SUN’S RAYS
Greenhouse gas increases through Industrial Age CO 2 – roughly constant at 280 ppm until 1800 – then rising rapidly to 380+ ppm today, and then rising rapidly to 380+ ppm today, and further yet. further yet. Methane – 800 ppb until 1800, now 1,750 ppb. now 1,750 ppb. Nitrous oxide 270ppb until 1800 – now 310 ppb Lower atmosphere ozone increased around 30% over the same period.
Addition of man-made factors to models duplicates observations
Q. Global Warming? Change between 1750 and 2000 A. Man-made gases dominate
Global warming - questions What is happening? What are the reasons? What is likely to happen from now on? What can we do?
Global warming What is happening? What are the reasons? What is likely to happen from now on? What can we do?
What is likely to happen from now on? Depends on what we do. Slowing down GHG emissions, particularly carbon, will mitigate future temperature rises – but there is a lot of momentum already embedded in the climate system. Adaptation will be needed for coming changes in – rainfall patterns - glaciers and sea-ice - sea-levels - land temperatures - food crop, forest and animal ranges - human impacts – livelihoods, wealth and health
Rainfall Glaciers and sea-ice Sea levels Land temperatures
Himalayan glaciers feed 7 of Asia’s great rivers - The Ganges - The Indus - The Brahmaputra - The Salween - The Mekong - The Yangtze - The Yellow river Himalayan glaciers - critical 2.3 billion people
Rainfall Glaciers and Sea-ice Sea levels Land temperatures
Sea ice – also melting 1.3 million km 2 Arctic ice lost since mid-70s