The Escalator

One of the most common misunderstandings amongst climate change "skeptics" is the difference between short-term noise and long-term signal.  This animation shows how the same temperature data (green) that is used to determine the long-term global surface air warming trend of 0.16°C per decade (red) can be used inappropriately to "cherrypick" short time periods that show a cooling trend simply because the endpoints are carefully chosen and the trend is dominated by short-term noise in the data (blue steps).  Isn't it strange how five periods of cooling can add up to a clear warming trend over the last 4 decades?  Several factors can have a large impact on short-term temperatures, such as oceanic cycles like the El Niño Southern Oscillation (ENSO) or the 11-year solar cycle.  These short-term cycles don't have long-term effects on the Earth's temperature, unlike the continuing upward trend caused by global warming from human greenhouse gas emissions.

The data (green) are the average of the NASA GISS, NOAA NCDC, and HadCRUT4monthly global surface temperature anomaly datasets from January 1970 through November 2012, with linear trends for the short time periods Jan 1970 to Oct 1977, Apr 1977 to Dec 1986, Sep 1987 to Nov 1996, Jun 1997 to Dec 2002, and Nov 2002 to Nov 2012 (blue), and also showing the far more reliable linear trend for the full time period (red).