Slide 18 of 30
Notes:
In the natural environment, the temperature near the Earth’s surface varies from day to day with the weather, but also from season to season and from year to year. Climate is measured by the statistics of typical weather.
This picture shows typical year to year variations of annual average temperature at one place in a mid-latitude continent, of about +/- 2 °F or +/- 1 ° C. With some imagination, one can perhaps detect a slight increase from the first to the second half of the record of at most 1 °F. However, this signal of possible global warming is almost undetectable within the short term variability. By this measure, global warming will have to be several times larger before it becomes obvious in people’s year to year experience.