When March feels like May and May feels like July, what does that mean for August and September?

 

The United States and the rest of the world may soon have to come up with new definitions for the seasons. The first quarter of 2015 has shaped up to be the hottest since record-keeping began in 1880, according to a report released Monday.

 

And while residents of the East Coast of the U.S. were spared, the month of March brought “record warmth spread around the world,” with an average temperature of 1.53 degrees Fahrenheit above the 20th-century average—making it the hottest March ever recorded.

 

The new figures, released by the National Oceanic and Atmospheric Administration, mean 2015 is on track to become the hottest year on record—a title currently held by the year 2014.

 

If the warming pattern holds true, 2015 will end up as just one more piece of evidence that shows the effect carbon emissions and greenhouse gases are having on climate change. Nine out of the 10 hottest years on record have come after 2000.

 

And those emissions just reached an all-time record too.

 

In March, researchers recorded the average global carbon dioxide emissions in the atmosphere as exceeding 400 parts per million for the first time in human history.

 

“This marks the fact that humans burning fossil fuels have caused global carbon dioxide concentrations to rise more than 120 parts per million since preindustrial times,” Pieter Tans, lead scientist of NOAA’s Global Greenhouse Gas Reference Network, said in a statement. “Half of that rise has occurred since 1980.”

 

The 400-ppm number isn’t significant for any particular reason—but it does signal the efforts it will take in carbon emission reductions to keep the figure down.

 

“Elimination of about 80 percent of fossil fuel emissions would essentially stop the rise in carbon dioxide in the atmosphere, but concentrations of carbon dioxide would not start decreasing until even further reductions are made, and then it would only do so slowly,” James Butler, director of NOAA’s Global Monitoring Division, said in a statement.

 

And if those cuts aren’t made, temperatures will continue to increase, sea-level rise will worsen, and the severity and frequency of storms will grow, as will the likelihood of decades-long mega droughts.