Global warming is happening so fast that scientists now say we'll cross a crucial temperature thresholdas early as 2030 — up to a decade sooner than previously thought — according to a sweeping new U.N.-sponsored review of climate science published Monday.

The big picture: Atmospheric CO2 concentrations were higher in 2019 than at any time in at least 2 million years, and the past 50 years saw the fastest temperature increases in at least 2,000 years, according to the new assessment by the Intergovernmental Panel on Climate Change (IPCC).

What they're saying: The report says that the connection between human emissions of greenhouse gases and global warming is “unequivocal.”

• It's the “strongest statement the IPCC has ever made,” Ko Barrett, the panel's vice chair and senior advisor on climate to the National Oceanic and Atmospheric Administration, told reporters.

Why it matters: Warming is affecting every area of the globe, making the world a more volatile place, and the report connects the dots between extreme events and long-term human causes.

• Weather and climate events are becoming more common and severe, it says, and rising sea levels are flooding coastal areas with regularity.
• It shows we’re running out of time to meet the targets of the Paris Climate Agreement.

Details: The IPCC looked at how long it will take the world to reach a temperature warming target of 1.5°C (2.7°F) compared to preindustrial levels and determined that could happen between 2030 and 2035.

• The 20-year period from now through 2040 will be the first to meet or beat that target, the panel found.
• Even under the lowest pathway of future greenhouse gas emissions, the 1.5-degree threshold would be exceeded for a period of time.

Only rapid, steep and sustained greenhouse gas emissions cuts, down to net zero and eventually net negative values, could avoid exceeding 1.5 or 2°C (3.6°F) of warming over the longer-term, the report states. The world has already warmed by 1.1°C (2°F) relative to the 1850-1900 average.

• The report also notes that many of the effects of climate change through 2050 are already locked in by the emissions to date, but there is still time to greatly reduce climate impacts later this century.

Yes, but: The world is nowhere near making the emissions cuts in line with the Paris Agreement targets, instead tracking toward at least 3°C (5.4°F) of warming, based on the latest emissions reduction pledges.

Between the lines: The peer-reviewed report, conducted by hundreds of authors around the world, arrives at a hinge point in the global fight against climate change.

• Leaders in the U.S. and European Union are seeking to enact strict new measures to cut greenhouse gas emissions and keep the 1.5-degree goal alive, with a pivotal summit slated for November in Glasgow. But consensus on emissions cuts among all of the wealthiest nations remains elusive.
• It also comes amid an outbreak of extreme weather events that have killed hundreds in the Pacific Northwest in a scorching heat wave, with devastating wildfires striking the U.S., Canada, Russia and the Mediterranean region this summer.
• The report touches on tipping points in the climate system, such as the shutdown of the Gulf Stream and collapse of part of the Antarctic Ice Sheet, categorizing them as low-risk but high-impact events.

Flashback: Compared with its first report in 1990, the IPCC’s new climate assessment reflects global warming's transition from a far-off, future issue to a present-day crisis.

• “The internationally agreed threshold of 1.5 degrees Celsius is perilously close,” U.N. Secretary-General António Guterres said in a statement. “We must act decisively now to keep 1.5 alive.” He called for the report to “sound a death knell for coal and fossil fuels, before they destroy our planet.”
• "The actions we take over the coming years is what will determine if we can get on the right path," Jane Lubchenco, the top climate official in the White House Office of Science and Technology Policy, told Axios. "So every action matters, every year matters, every fraction of a degree matters."

By the numbers: The report projects that global warming at the end of the century will range between about 1.3 to 5.7°C (2.34 to 10.26°F), relative to 1850-1900 levels, depending on greenhouse gas emissions.

• Regional temperature changes, however, will far exceed global averages, especially in the Arctic.
• Sea levels are projected to increase under the intermediate to high emissions pathways by between at least a foot and a half to more than three and a half feet by the end of the century.
• A rise of 7 feet by the year 2100, or even 16 feet by 2150, “cannot be ruled out,” due to uncertainties about potential tipping points involving Antarctic ice melt.
• The report warns of the occurrence of “compound events,” in which various extremes, such as heat waves and drought, overlap and affect society in unprecedented ways.
• It also makes clear how starkly different the current climate already is from that in which modern human civilization first thrived.

What we're watching: The report will heavily influence diplomatic efforts to secure new emissions reduction commitments from major emitters at Glasgow. It's also likely to further galvanize climate activists. A 2018 IPCC report gave rise to the global youth-led climate movement.