The campaign, which was first launched in 2007, is being handled for the Department of Energy and Climate Change (DECC) and the Department for Transport (DfT).
Forster resumes working on the Act on CO2 brief after being involved it in its launch. After the launch, the brief was taken in-house.
The campaign was won in a competitive pitch managed by the Central Office of Information (COI), as revealed in PRWeek (24 July).
Forster beat two other agencies to work on the behaviour change campaign. The aim of the campaign is to engage the public on climate change issues and encourage them to take steps to reduce their carbon footprint. Steps being encouraged could include car-sharing and turning off taps.
The campaign is based on research that showed, despite being aware of climate change, people felt a sense of powerlessness in being able to make a difference and were confused by the plethora of messages around the subject.
The agency expects the campaign to be media relations led, with a social media element.
Project director Cheryl Campsie will lead the five-strong account team at Forster, reporting to DECC head of strategic marketing Fiona Samson.
The news follows last week's climate change camp, held in London by environmental activists. The protesters called for more action to be taken against CO2 emissions, in the run up to the UN climate change conference in Copenhagen in November. The camp organisers singled out 'empty government rhetoric and corporate spin' for criticism on their website.
Forster project manager Vicky Argles revealed part of the brief would focus on showing people that the Government was actively fighting climate change.
Argles said: 'We will want to use this as an opportunity to show what the Government is doing itself, to inspire people to do their own bit.'
Separately, Forster has been awarded a contract by NHS South East Coast and NHS South Central to plan and run the Big Drink Debate project, after a competitive pitch. The debate will aim to discover the region's attitude to alcohol, how much people consume, and how they perceive alcohol-related health.
HOW I SEE IT - Vicky Argles, Project manager, Forster
We worked on the Act on CO2 campaign before, with the Department for Transport, but this is a little bit different. We were trying to bridge the gap between what people do every day and the big impact that it has on climate change, explaining the issues and consequences of climate change to spur them into action. It is more about education, than just raising awareness.
One challenge will be achieving cut-through in the media in the run up to the climate conference in Copenhagen in December, as lots of people will be talking about climate change in the coming months.