evidence: Most of these models are long since obsolete, replaced by far more advanced generations. And yet, most of them were spot on in their projections of how much the Earth would warm in the years after they were published in response to greenhouse gas emissions. Fourteen out of 17 models were found to be accurate. The new study highlights a critically important, but sometimes overlooked, point about the way climate models work. The amount of warming they predict is a direct consequence of the greenhouse gas emissions they assume for the future. And accurately predicting carbon emissions is notoriously difficult—it depends on many human factors, including population growth, economic shifts and changes in the energy landscape. [...] One example is a famous climate model developed by NASA researcher James Hansen, whose congressional testimony on climate change in the 1980s helped catapult the issue into the public spotlight. Hansen’s 1988 model ultimately predicted about 50% more warming for the coming decades than actually occurred, giving fodder to skeptics’ arguments that scientists were exaggerating the issue of global warming.