Most of these graphs show global, northern hemisphere and southern hemisphere land and ocean temperature anomalies using data downloaded from the National Oceanic and Atmospheric Administration (NOAA) and National Climatic Data Center (NCDC) of the U.S. Department of Commerce, available here. The “temperature anomalies” are differences from the 20th century average (1901-2000).
Northern Hemisphere values are coloured blue, Southern Hemisphere values are in red and the combined values are in black. The jagged curve is the 5 year running average displaying the average global value for the prior 60 months. It is clear that warming has continued to increase over the last century with a slight decline during and after the second world war and a very recent slowdown apparently caused by an unusually cold La Niña period.
You’ll find many more graphs showing other details on this page. All of the graphs and the “raw” data are available on request for download in *.xls spreadsheet form. You can see a full-sized picture for any of these graphs by clicking on the image; it should open in a separate window or tab, depending on your browser.
Land temperatures are green, ocean temperatures are blue and the combined values are red. These are month by month sliding averages of the preceding 30 years, the interval which the WMO uses to describe “climate”.
These are 12-month numbers, each month for the preceding 12 months, to filter out seasonal variations.
This graph shows the rate of change of temperature globally, looking at the 30 years leading up to each month and calculating a linear least squares fit to the slope (rate of change) for that interval. It shows clearly that there is a continuing long-term warming although there are periods when the warming slows down. (A negative number would indicate cooling). Natural decadal variability is responsible for the ups and downs, as expected (see the study by Swanson, Tsonis et al cited on the page “The Cooling Myth“) and it occasionally masks or exaggerates the long-term trend. Figures 4 – 7 on the “Greenhouse Gases” page show more detail and separates the two factors.
The global combined sea-surface and land-surface air temperature for 2008 was cooler than most recent years, largely owing to a strong La Niña. This is characterized by unusually cold ocean temperatures in the equatorial Pacific Ocean. La Niña developed during summer 2007 and reached its peak strength in early 2008.
The following graphs show the RSS satellite temperature measurements for the lower and middle troposphere (the two lowest layers of the atmosphere) and the stratosphere (the top layer). Contrary to the “contrarian” mythology, there is no statistically significant decline in the tropospheric temperature anomalies and the decline in the stratospheric temperatures is as predicted, confirming that greenhouse gases are causing the temperature changes.