There’s a very small but distinct possibility that rapid global warming could pose an “existential threat” to the survival of humans by 2050, UC San Diego said Thursday in one of the most dire forecasts yet about climate change.

The school’s Scripps Institution of Oceanography published a paper that said there is a 5 percent chance of catastrophic change within roughly three decades, and a smaller chance that it would broadly wipe out human life.

Scripps made the claim while proposing two new classifications for climate change: catastrophic and unknown, or existential.

Catastrophic means that most people would have trouble adapting to such change. The latter terms means that they would not be able to.


“Other people have used the word catastrophic, but I have resisted doing so until now,” said the study’s lead author, Veerabhadran Ramanathan, a renowned climate scientist who helped influence Pope Francis to urge the world to fight global warming in 2015.

“I changed my mind because, over the past five years, I have gone back and reviewed data that we began collecting from satellites in the 1980s and data from aircraft and changes in the intensity of storms, and studies about the possible health affects of rapid global warming.

“There is a low probability that the change will be catastrophic. But you would not get on an airplane if you thought there was a 5 percent chance that it was going to crash.”

He noted that the probability of an existential threat is even smaller, but said, “that chance rises to 20 to 30 percent by 2070.”


Ramanathan published his findings Thursday in the journal Proceedings of the National Academy of Sciences. The study was co-authored by Texas A&M University researcher Yangyang Xu, who is Ramanathan’s former graduate student.

They also released their findings in a news release that included remarks from California Gov. Jerry Brown, who said, “This report shines a bright light on the existential threat that climate change presents to all humanity.

“Scientists have many ideas about how to reduce emissions, but they all agree on the urgency of strong and decisive action to remove carbon from the economy.”

The always controversial topic of climate change has become especially intense recently due to hurricanes Harvey and Irma.


Many scientists and some politicians say such storms might become more frequent in the future due to the influence of global warming.

Miami Mayor Tomás Regalado, a Republican, told the Miami Herald that, “This is the time that the president and the EPA and whoever makes decisions needs to talk about climate change.”

“If this isn’t climate change, I don’t know what is. This is a truly, truly poster child for what is to come.”

Such comments displeased EPA Administrator Scott Pruitt, who said that it was inappropriate to focus on the issue while Florida was trying to cope with Irma.


Pruitt previously said that he did not agree that people’s use of fossil fuels — which create carbon dioxide — is chiefly responsible for climate change.

He told CNBC, “I think that measuring with precision human activity on the climate is something very challenging to do and there’s tremendous disagreement about the degree of impact.”


Science Playlist × On Now In a first, scientists rid human embryos of a potentially fatal gene mutation by editing their DNA On Now Space station flyovers visible from San Diego this week 0:55 On Now UCSD's 'ghost drivers' begin testing people's reaction seemingly empty cars 1:29 On Now 10 interesting facts about Mars On Now Kids can add years to your life On Now LA 90: SpaceX launches recycled rocket On Now Big passions, big giving: Malin Burnham 2:30 On Now Big passions, big giving: Darlene Shiley 2:40 On Now Big passions, big giving: Joan and Irwin Jacobs 2:45 On Now Ocean temperatures warming at rapid rate, study finds

Twitter: @grobbins

gary.robbins@sduniontribune.com