The world is increasingly likely to see a year in which global average surface temperatures meet or exceed the Paris Agreement's ambitious temperature target of 1.5°C (2.7°F) above preindustrial levels, a new report predicts.

Why it matters: Limiting warming to 1.5°C is an existential matter for small island states, which could be swamped by rising sea levels if temperatures climb higher. While a single year would not indicate the treaty's 1.5-degree target has been exceeded permanently, it would be a significant milestone.

• The report serves as another indication that the world is running out of time to limit global warming to levels that society and natural systems can tolerate.
• Based on recent emissions trends, temperatures are on course to reach or possibly exceed 3°C (5.4°F) above preindustrial levels by 2100.

Yes, but: When it comes to taking stock of global warming, what matters are trends over decades, not individual years.

• Still, optics nonetheless matter with these climate thresholds, and even temporarily reaching or exceeding the 1.5-degree target would likely be seen as an indication of the urgency for action to slash emissions of planet-warming greenhouse gases.

The big picture: Studies have shown that limiting global warming to 1.5°C above preindustrial levels would have a much greater chance of avoiding potentially disastrous outcomes. These include the widespread loss of coral reefs and triggering runaway feedback loops, such as the collapse of large parts of the Antarctic Ice Sheet.

Details: The report, led by the U.K. Met Office with the participation of scientists from the U.S. and other nations and distributed via the U.N.'s World Meteorological Organization (WMO), says there is a 40% chance that the 1.5-degree target will be temporarily reached in at least one of the next five years.

By the numbers: The analysis pegs the likelihood at 90% that at least one year during the 2021-2025 period will be the warmest on record, knocking 2016 and 2020 out of the top spot (the two years were virtually tied).

• The chance of temporarily bumping up against the 1.5°C temperature anomaly "has roughly doubled" compared to last year's predictions, the report says — an indication that time is quickly running out to avoid hitting or exceeding the target over a longer time period.
• However, it's unlikely 2021 will be the one to set the next warmest-year record, given the lingering influence of a waning La Niña episode in the tropical Pacific Ocean.
• The report, known as the "Global Annual to Decadal Climate Update," finds that the annual global average temperature is likely to be at least 1°C (1.8°F) above preindustrial levels (defined as the 1850-1900 average) during each of the coming five years, ranging from 0.9°C to 1.8°C.
• Of note: For now, the report finds, it's "very unlikely" that the five-year period will have an overall average temperature departure from average of 1.5°C or higher.

What they're saying: "This study shows, with a high level of scientific skill, that we are getting measurably and inexorably closer to the lower target of the Paris Agreement on Climate Change," said WMO secretary-general Petteri Taalas in a statement.

• "It is yet another wakeup call that the world needs to fast-track commitments to slash greenhouse gas emissions and achieve carbon neutrality," he said.