The level of carbon dioxide, a long-lived gas that warms the planet, in Earth's atmosphere hit a new official record this spring and is now more than 50% higher compared to preindustrial times, new data released Friday shows.

Why it matters: Carbon dioxide levels rose to a peak of 421 parts per million in May, for the highest level in human history, according to the National Oceanic and Atmospheric Administration and the Scripps Institution of Oceanography. The increase compared to 2020 was 1.8 ppm, a slight drop from last year.

Threat level: Increasing CO2 levels are already having severe consequences.

• These include more frequent and extreme heat waves around the world, heavier precipitation events, stronger and wetter hurricanes, more frequent and larger wildfires, as well as an acidification trend in the world's oceans and marine heat waves that have repeatedly battered Australia's Great Barrier Reef and other ecological treasures.
• Carbon dioxide levels are already the highest they've been since well before the beginning of human history. At the start of the industrial revolution, they were around 280 ppm.

The big picture: The pace of the increase in planet-warming gases is staggering compared to the course of Earth's history, according to Pieter Tans, who tracks greenhouse gases for NOAA.

• Coming out of the last ice age, CO2 went up by about 80 ppm during the course of 6,000 years. Yet now it's increasing by more than 2 ppm "every single year," he said.
• The 400 ppm milestone was eclipsed in 2013, and 440 ppm could be reached in a decade. In an April interview with Axios, he described the growth rate as "an explosion" from a geological perspective.
• "Carbon dioxide is at levels our species has never experienced before — this is not new," Tans said in a statement Friday. "We have known about this for half a century, and have failed to do anything meaningful about it. What's it going to take for us to wake up?"

What they're saying: "The science is irrefutable: humans are altering our climate in ways that our economy and our infrastructure must adapt to," said NOAA administrator Rick Spinrad, in a statement. "We can see the impacts of climate change around us every day."

• According to a statement from NOAA and Scripps that is supported by scientific studies, today's CO2 levels are now comparable to a period known as the Pliocene Climatic Optimum, between 4.1 million and 4.5 million years ago.
• During that time, sea levels were far higher than they are today, at heights that would swallow modern cities, and global average temperatures were about 7°F above preindustrial levels.