Quote:
Originally Posted by wildsage  From the IPCC:
"Although natural internal climate processes, such as El Niņo, can cause variations in global mean temperature for relatively short periods, analysis indicates that a large portion is due to external factors. Brief periods of global cooling have followed major volcanic eruptions, such as Mt. Pinatubo in 1991. In the early part of the 20th century, global average temperature rose, during which time greenhouse gas concentrations started to rise, solar output was probably increasing and there was little volcanic activity. During the 1950s and 1960s, average global temperatures levelled off, as increases in aerosols from fossil fuels and other sources cooled the planet. The eruption of Mt. Agung in 1963 also put large quantities of reflective dust into the upper atmosphere. The rapid warming observed since the 1970s has occurred in a period when the increase in greenhouse gases has dominated over all other factors.
Numerous experiments have been conducted using climate models to determine the likely causes of the 20th-century climate change. These experiments indicate that models cannot reproduce the rapid warming observed in recent decades when they only take into account variations in solar output and volcanic activity. However [...] models are able to simulate the observed 20th-century changes in temperature when they include all of the most important external factors, including human influences from sources such as greenhouse gases and natural external factors. The model-estimated responses to these external factors are detectable in the 20th-century climate globally and in each individual continent except Antarctica, where there are insufficient observations. The human influence on climate very likely dominates over all other causes of change in global average surface temperature during the past half century." |
Interestingly, I note several subtle changes in wording. Climate change replaces warming when it's noted that temperatures leveled off, cooled, and warmed all due to man-made influences. Aerosols are seen to level temperatures off, yet are touted as causing warming. The rise in temperatures noted earliest in the 20th century are, by any reasonable estimation, long preceding the man-made global warming gas emissions. Temperature variations THEN are due entirely to natural effects (assumed as solar activity in the explaination above), but later in the 20th century, models can't say the same thing? And, the global rise in temperatures noted above starts in the 70's. 30 years of global warming makes a trend?
Nothing from the IPCC makes sense, when looked at with a skeptical, logical lens.