What is being published on Friday?

The summary of the first part of the so-called fifth assessment report (AR5), which focuses on the scientific evidence behind climate change and the human role in it. The IPCC has been meeting in Stockholm this week to discuss the final wording of the summary of Working Group One (WG1), which assesses the physical science, such as concentrations of greenhouse gases in the atmosphere, temperature rises and climate models. It has been written the world’s top climate scientists – 209 lead authors and 50 editors from 39 countries – and will be presented to governments and the public at 9am on Friday. This summary report will be followed by WG1’s full in-depth report on Monday, 30 September.

What will it say?

Early drafts indicate that scientists have revised upwards the certainty that human activities are driving the warming the world has experienced, from “very likely” or 90% confidence in 2007, to “extremely likely” or 95% confidence now. It will also include new projections for future sea level and temperature rises.

How does the IPCC work?

Scientists have spent the last few years – on a voluntary basis – collating and summarising peer-reviewed climate science. The IPCC does not produce original work itself, but summarises what has already been published in scientific journals. It has a small secretariat of a dozen staff, based in Geneva, Switzerland. The IPCC chairman is Rajendra Pachauri, who was appointed in 2002 and re-elected in 2008.

Do these reports still matter?

Yes. The IPCC’s major assessments are extremely influential and widely read. The science in the reports underpins the crucial UN climate negotiations on political efforts to tackle climate change. But many people, including some of the scientists who put together the reports without pay, say that more targeted and more frequent reports would be more useful.

What isn’t included in this week’s report?

The other two main parts of AR5, which will be published in 2014.

Working Group Two (WG2) examines the impacts of climate change, and how plants, animals and humans can adapt, such as by building flood defences and adapting farming practices.Working Group Three (WG3) concentrates on climate mitigation – efforts to mitigate the most extreme scenarios of warming by cutting greenhouse gas emissions from power stations, factories, cars, farming and other human activities.

Source: www.theguardian.com