Columbia University's James Hansen, a well-known activist and climate scientist, recently led a study, then published a paper, addressing this debatable limit, stating that 2 degrees of global warming would "subject young people, future generations and nature to irreparable harm". Such harm would include consequences such as widespread sea-level rise, mass extinction, and a change in cloud cover of the planet.

Researchers from a range of fields contributed to this study, making it more widely received and understood by the general public, and giving it a different feel from the typical climate science paper. Inputs from economists and policy-makers are included, as well as a statement claiming that humans currently have a moral obligation to slow and possibly reverse current warming trends for future generations' wellbeing.

In reference to probable flooding of coastal cities in the future, Hansen bluntly stated, "We can't accept that. If we have any love for our children and grandchildren, we can't accept that."

Since the beginning of the industrial era, humankind has added roughly 370 gigatons of carbon (GtC) into the atmosphere, with rates accelerating as populations continue to rise and coal continues to be consumed in large countries such as China. This trend is reflected in what Hansen said, "It seems like we're just charging ahead, burning any and every fossil fuel. There seems to be no real effort to get off that business-as-usual path".

One over-arching message resounds throughout Hansen's study – if reductions in fossil fuel consumption and greenhouse gas emissions in an aggressive and immediate manner, there is no feasible way in which the 2 degree increase in global temperatures will be avoided by the year 2100.