WASHINGTON (CBS DC) — Due to a complex system of measuring, a new study finds that global warming has been overestimated over the past 20 years.
According to the study from the University of Victoria, British Columbia, simulated climate models have combined a series of errors in external forcing and internal climate variability to show that global warming has progressed much faster than in reality.
The researchers write that the global mean surface temperature rose at a rate of .14 degrees Celsius per decade over the past 20 years – a rate of warming which is significantly slower than that simulated by modern climate models.
In the past 15 years, the observed trend is more than four times smaller than the average simulated numbers.
A series of variations – including the global warming seen from the 1998 El Nino event – disrupt the calculations between simulated and observed effects of global warming.
Another possible driver of the difference between observed and simulated global warming is increasing stratospheric aerosol concentrations. Results from several independent datasets show that stratospheric aerosol abundance has increased since the late 1990s, owing to a series of comparatively small tropical volcanic eruptions.
The study finds that, as a whole, the climate system is so complex that “there will always be uncertainties in assesments and projections of climate change.”