As world leaders prepare for climate talks in Paris at the end of November, Nasa satellites have been flying around Earth tracking rising carbon dioxide levels, which scientists say are driving climate change. They include the new Orbiting Carbon Observatory-2 (OCO-2) satellite.

OCO-2 was launched in 2014 and is designed to give scientists a fuller picture of the effects of increases of carbon in the atmosphere. It charts some 100,000 measurements across the globe daily and can detect even slight changes, according to Nasa scientist Dr Annmarie Eldering.

"We seek to use these OCO-2 measurements to find out about where the carbon dioxide take up is, how it changes from season to season, and from year to year," she explained. "Really we're pretty focused on trying to understand a few basic things. Like when we have a drought in the US, how much do the trees reduce their uptake of carbon dioxide? When it's extra rainy in some part of the world, how much does that increase the uptake of carbon dioxide?"

One of her concerns is that oceans and forests will become too saturated amid rising CO2 levels. According to Nasa, excess carbon dioxide levels act as a blanket, trapping heat in the atmosphere, which in turn spurs major changes to the climate. Examples include rising sea levels and extreme weather.

Earlier this month, the World Meteorological Organization announced that greenhouse gas levels in the atmosphere had reached a record high in 2014. The UN agency's data showed levels of carbon dioxide, the main greenhouse gas, climbing steadily towards the 400-parts-per-million (ppm) level, having hit a new record every year since reliable records began in 1984. With the help of the OCO-2 satellite, Eldering said she hoped her research would help policy makers make scientifically sound decisions going forward.

"There's no doubt our emissions are driving this climate change and we need to have coordinated efforts across the board to reduce those carbon dioxide emissions," she said. "We can see the world changing around us, and the impacts of the climate change, so this is really an important topic to address."

World leaders are scheduled to meet at the UN climate summit in Paris from 30 November to 11 December, where they will aim to map out a global accord to limit greenhouse gas emissions.