THE world's leading atmospheric scientists publish today the most comprehensive report on the state of the planet's climate, and it makes for grim reading.

The Intergovernmental Panel on Climate Change (IPCC), set up in 1988 by the UN to study the world's climate, has released its fifth Assessment Report; its first in six years. The document, which runs to thousands of pages, and has received contributions from more than 800 scientists in 85 countries, is the clearest warning yet of the risk humans face from self-inflicted climate change.

Such is the scale of the undertaking that keeping the report's findings a secret has been impossible. Leaks have flowed like melt-water from Arctic sea ice. The primary finding is that scientists are now 95 per cent certain that climate change is being driven by human activity, up from 90 per cent in 2007, and 66 per cent in 2001. This is now at the level of confidence usually accepted as the criterion for scientific certainty.

Today's report, the first of three parts to be released over the next six months, is expected to reveal that global surface temperatures, which have risen by nearly one degree in the last century, could rise by up to 4.8°C by 2100, if we do not take urgent action now.

Snow and ice cover has decreased, and sea levels, which rose by 19cm in the 20th century, could rise by an extra 26 to 81cm by the end of this century, which would threaten coastal regions. The report will also say that weather patterns are becoming more extreme and unpredictable, while the acidification of the oceans is wrecking coral reefs.
 

IN THE Copenhagen Accord in 2009, governments promised to prevent the rise of global temperature by 2°C above pre-industrial levels. This is the level beyond which "dangerous climate change" is predicted, the Accord says. But, as the temperature rise already stands at 0.8°C, significant carbon-emission cuts are needed, if such a scenario is to be avoided.

The new report also tackles the apparent slowdown in warming since 1998, something that climate-change deniers have seized on as proof that there is nothing to worry about. Satellite measurements of the solar radiation entering the atmosphere have shown that the planet continues to get warmer, however, and the IPCC report is expected to point to the oceans as absorbing more of this heat. This has also coincided with the El Niña weather system, a cooling effect that, when combined with the other factors, accounts for much of this apparent slowdown.

Climate-change deniers can fudge the science, and try to convince the world that the risk of doing nothing is worth taking, but already international development agencies deal daily with people whose lives are blighted by climate change. Perversely, these tend to be the poorest and most vulnerable communities, who have done the least to create the misery now confronting them.
 

THE story is the same in many parts of the world. In Malawi, weather patterns have become more erratic over the past 30 years, as flash-flooding and drought are making farming increasingly difficult. In Bolivia, increased temperatures have led to new pest invasions, which require expensive crop-spraying, while water shortages have led to conflicts and migration.

Bangladesh has been on the receiving end of both more extreme and unpredictable weather and sea-level rise. Mofazzal Kagzi, aged 69 and a fisherman from Jhalokati, says: "Farming used to be a good living. People had goats, cows, rice, and fruit trees to feed their families. Now, because of climate change, this is not possible. The weather is worse than before, when we used to have six seasons. Everything was going well. But now there are changes. Too much rain, then drought, then heat."

Helping people on the front line in Bangladesh is the Christian Commission for Development in Bangladesh (a Christian Aid partner organisation). Its director, Joyanta Adhikari, says: "It's not only governments, not only civil society; it's the Church which needs to come together and raise its voice. Politicians nowadays think only of their tenure - just four or five years. They don't look beyond that. Although the pinch of the problem has not been felt in the Western world, the day will come when everybody will be affected.

"We have enough in this world to meet our need, but we don't have enough to meet our greed."
 

A GROWING number of Christians around the world are waking up to their duty to speak up for the poor and vulnerable - for our generation, the "widows and orphans" of James 1.27 - suffering from a climate changed by our indulgent, industrialised excess.

But there is more that could be done. The Church has a powerful voice, in terms of both a public platform, and a motivated body of believers. Christians can write to their MPs, join campaigns, and support organisations striving to tackle climate change. Pressure can also be brought to bear on companies that continue to pollute, in which individual Christians and churches have invested money.

Ultimately, we need our self-proclaimed "greenest government ever" to ensure that its own energy policy is in order, so that it can put pressure on others to make significant emissions cuts.

This means halting the shale-gas industry in its tracks, and starting to invest instead in a sustainable-energy future. Britain has huge renewable-energy resources, and a recent survey by Cardiff University suggested that public support for solar (85 per cent) and wind power (75 per cent) remains strong, despite negative press.

Today's IPCC report makes the science clear. We now must seize the opportunity to speak with a prophetic voice, and accept the moral duty to act, to secure the planet for future generations.

Joe Ware is a church and campaigns journalist at Christian Aid.