World leaders will hold the biggest-ever meeting on climate change next month in Copenhagen, hoping to finally strike a global deal on curbing carbon emissions. As negotiators race against the clock, here's a rapid-fire refresher on how we got to this point.
Climate change is a slow train that's been coming for more than a century, but even slow trains eventually reach their destinations. With ocean temperatures hitting record highs this summer, Arctic sea ice dwindling and glaciers melting faster than ever, that train now seems to be pulling into the station — and the urgency is suddenly hitting home for people all around the planet. 
Just as this global awareness is gaining momentum, so is the global effort to stop climate change in its tracks. When world leaders meet in Copenhagen for 10 days this December — a summit designed to replace the historic but hobbled Kyoto Protocol, which starts expiring in 2012 — it will be the culmination of years spent listening, bickering and compromising over various countries' greenhouse gas emissions, which trap heat from the sun and warm up the planet. From the 1972 Stockholm Conference to the '92 Earth Summit to smaller-scale meetings like last year's in Poznan, Poland, climate negotiators have been working for decades to reach this stage of the war on warming. 
They still have a long way to go, too, with the United States' good-faith domestic climate bill sputtering in the Senate, and developing nations like China and India still balking at the idea of mandatory emissions cuts. But the international debate has at least grown less heated in the 12 years since Kyoto, even if the planet hasn't, and many observers see the upcoming Copenhagen summit as the best remaining chance to stop a runaway train before it's too late.
Check out the timeline above for a quick rundown on the context behind climate change — from how we got into this mess to how we're trying to dig out of it — and stay tuned to MNN for ongoing coverage of December's Copenhagen climate talks, including the next three installments in our four-part series on "The Road to Copenhagen." 
The Road to Copenhagen: A brief history of climate change
As world leaders negotiate a global treaty on climate change, here's a refresher on how we got into this mess, and how we're trying to dig out of it.