claim: Internal variability can only account for small amounts of warming and cooling over periods of decades, and scientific studies have consistently shown that it cannot account for the global warming over the past century.
evidence: Climate is the statistics (usually, mean or variability) of weather: the classical period for averaging weather variables is 30 years in accordance with the definition set by the World Meteorological Organization.Instrumental temperature records have shown a robust multi-decadal long-term trend of global warming since the end of the 19th century, reversing longer term cooling in previous centuries as seen in paleoclimate records.
category: Global warming hiatus