My, how things have changed! In 2000, scientists from the Worldwatch thinktank in Washington teamed up with the UN to spot the greatest threats to the planet over the coming years. Top of the list was ecosystem collapse, such as deforestation and the demise of corals; second were health and diseases, such as Sars and Aids; and third was global poverty. The world's top environmental analysts gave climate change only four paragraphs in an eight-page essay – little more than malaria, trade, air pollution, population, fresh water or food supplies. Carbon emissions, they reported, were "continuing to decline" and global temperatures were "steady".

How quaint. Ten years later, climate change is equal top of the international agenda. The world is locked into insanely complex talks to reduce emissions, and green groups and government shout as one that we have only a few years to avoid apocalypse. The polar bear on the melting ice flow has become an iconic picture of the decade, business has painted itself green, we've changed our lightbulbs and wind power has taken off. As Al Gore – in 2000 the new presidential nominee of the Democratic party – said, "We are all environmentalists now."

All this in a decade? What on earth happened?

Climate change took off on the back of science and a storm of weather-related disasters. The huge floods in Mozambique that displaced millions of people in January 2000 laid down a marker of what was to come. Within months, India was struck by one of its worst droughts, and 4.5 million people were made homeless by floods in Cambodia and Thailand. By 2003, record numbers of cyclones, hurricanes, heatwaves, droughts, fires, whirlwinds and floods killed tens of thousands of people.

It took record temperatures in Britain and 30,000 people to die in the 2003 European heatwave to bring climate change closer to home, but what perhaps clinched the big idea that Earth was in trouble was the 2004 Indian Ocean tsunami, which killed more than 300,000 people. It had nothing to do with global warming but it reinforced the idea of the power of nature. Eight months later, Hurricane Katrina swept away parts of Louisiana along with much of the US's scepticism for climate change.

Meanwhile, more studies linked weather extremes to man-made emissions. Isolated contrarians claimed warming was natural, linked to sunspots and would be good for growing grapes in Britain. But in 2007 the Met office announced that 11 of the last 13 years had been the warmest on record, while a consensus of 2,000 UN climate scientists said climate change was not just "unequivocal" but most of it was man-made.

Corporate greenwash reached new heights in 2000, with BP rebranding itself Beyond Petroleum and the global nuclear industry calling itself "environmentally indispensable". The action then moved to Wall Street and the City; by 2007, Lehman Brothers in New York had set up an internal global council on climate change, and the same companies that had grown fat financing opencast coal mines, oil rigs and SUV plants began advising clients to Get Into Green.

In 2006, Nicholas Stern, a former World Bank economist at the UK Treasury, reported that business as usual in a climate-changing world meant economic meltdown. Politicians, industry, bankers and the media jumped aboard the green express, seeing dollar signs in emerging carbon markets and new technologies.

In fact, several other important events defined the environmental decade. One was China, which in 2008 officially overtook the US as the world's biggest greenhouse gas emitter. Its dash for development matched the west's consumption boom, and sucked in forests, minerals and fuel from all over the world. But by mid-decade its scientists and politicians had seen the plunging water tables, choked on the coal pollution and realised that it could not continue. China now leads the world in rolling out technological solutions.

Over the decade the world's population grew from just over 6.1 billion to about 6.9 billion. That increase is equivalent to nearly 12 new Britains, or three new Americas, or a new Africa; or almost exactly the number of people alive in 1750. The majority were born in the poorest countries, off the west's radar, but it's clear that population and climate will define the centuries ahead,

As 2009 ends, the climate situation appears to be worse than anyone had thought, with 4C temperature rises a certainty within 50 years if nothing changes. But like the calm before the storm in 2000, temperatures are steady and carbon emissions are falling because the recession has temporarily reduced industrial production and consumption.

So what about deforestation, the decline of coral reefs, the loss of fresh water, the rise of global diseases, pollution and all that poverty the UN feared?

Oh yes, they all got worse. But at least we can blame climate change now.