0546 GMT January 28, 2022
The last time that the nations of the world struck a binding agreement to fight global warming was 1997, in Kyoto, Japan. As leaders gather for a conference in Paris to try to do more, it's clear things have changed dramatically over the past 18 years, AP reported.
Some differences can be measured: Degrees on a thermometer, trillions of tons of melting ice, a rise in sea level of a couple of inches. Epic weather disasters, including punishing droughts, killer heat waves and monster storms, have plagued Earth.
As a result, climate change is seen as a more urgent and concrete problem than it was last time.
"At the time of Kyoto, if someone talked about climate change, they were talking about something that was abstract in the future," said Marcia McNutt, the former US Geological Survey director who was picked to run the National Academies of Sciences.
"Now, we're talking about changing climate, something that's happening now. You can point to event after event that is happening in the here and now that is a direct result of changing climate."
Other, nonphysical changes since 1997 have made many experts more optimistic than in previous climate negotiations.
For one, improved technology is pointing to the possibility of a world weaned from fossil fuels, which emit heat-trapping gases. Businesses and countries are more serious about doing something, in the face of evidence that some of science's worst-case scenarios are coming to pass.
"I am quite stunned by how much the Earth has changed since 1997," Bill Anderegg from Princeton University said in an email.
"In many cases (e.g. Arctic sea ice loss, forest die-off due to drought), the speed of climate change is proceeding even faster than we thought it would two decades ago."