A long-anticipated report from the United Nations’ Intergovernmental Panel on Climate Change reinforces earlier conclusions that global warming is both real and caused by human activity. In a first, the panel also recommended a ceiling on carbon emissions.

This is the panel’s fifth report; it’s the work of 259 scientists from 39 countries. The report sets out four different scenarios; three of those predict at least a 1.5 degree Celsius global surface temperature change by the end of this century, compared to preindustrial levels. This will also lead to more frequent and longer heat waves in many regions, flooding and droughts. The report predicts as the ocean warms, sea ice will continue to melt, and the sea level will begin rising faster than it has over the past 40 years.

Gerald Meehl is a climate scientist who’s been working on the IPCC reports since they began in 1990.

“Even in 1990 we had some fairly compelling evidence that by putting more CO2 and other greenhouse gases in the atmosphere we’d see some fairly significant changes in the climate,” he said. “I would have thought that 23 years later, that more would have happened to address this problem.”

The report also recommends the world set a limit on carbon dioxide emissions, because when the world passes one trillion tons of carbon emissions, warming will be more drastic.

From The New York Times:

Just over half that amount has already been emitted since the beginning of the Industrial Revolution, and at current rates of energy consumption, the trillionth ton will be released around 2040, according to calculations by Myles R. Allen, a scientist at the University of Oxford and one of the authors of the new report. More than 3 trillion tons of carbon are still left in the ground as fossil fuels.

Limiting the warming to the agreed-upon target “is technically doable, but at the moment we’re not going in the right direction,” Dr. Allen said in an interview. “I don’t think we’ll do it unless we bite the bullet and start talking about what we’re going to do with that extra carbon that we can’t afford to dump into the atmosphere.”

To keep using fossil fuels beyond the trillionth ton of emissions, companies would have to develop potentially expensive technology to capture carbon dioxide from emissions sources like power plants and store it underground. Such efforts have been lagging badly; only last week, Norway scaled back one of the most ambitious such projects because of soaring costs.

In the report, the scientists also increased their confidence that humans are the main cause of climate change since the 1950s—they’re now 95 percent sure.

Erica Peterson reports on energy and the environment for WFPL. She is also Enterprise Editor.