U.S. President Barack Obama's anticipated unveiling of new clean energy goals August 3 comes as the world prepares for a key climate-change summit late this year. We look at where the five biggest global greenhouse emitters stand today.
China is the world's largest emitter of greenhouse gases, contributing 27.6 percent of total global emissions in 2013, according to the latest available data. In the past, China often argued at global climate summits that it was too impoverished and undeveloped to commit to reducing its emissions, which come mainly from using coal to power its rapid economic rise. But in recent years, Beijing has changed policy and this year put forth ambitious goals that it will bring to the UN climate-change summit that will take place in Paris from November 30 to December 11.
China says it is aiming for its carbon-dioxide emissions to peak around 2030 and begin falling thereafter. To assure that happens, Beijing plans to progressively reduce its carbon dioxide emissions per unit of Gross Domestic Product (GDP) by 60 to 65 percent compared to 2005 levels over the next 15 years. The per unit measure reflects how much energy is used to manufacture goods so, in short, China is promising to become far more energy efficient than it is today.
Edward King, editor of Responding to Climate Change (RTCC), a London-based news and analysis website on international climate policy, says the Chinese approach is typical of that favored by many developing economies today.
"It doesn't necessarily mean that the overall emissions are going to be coming down [immediately]," King says. "It does mean that, per unit, it is going to try to make [its energy use] more efficient and that is the type of pledge that leading developing countries like China, like India, made in 2009 in Copenhagen at UN talks and are likely to make again in Paris."
The United States
The world's second biggest greenhouse gas emitter is the United States, contributing 14.5 percent to the world total. Washington has said ahead of the Paris summit that it plans to cut its emissions by 26 to 28 percent on 2005 levels by 2030 and President Obama's anticipated unveiling of new clean energy goals on August 3 looks intended to help ensure that happens.
Obama's Clean Power Plan to be announced August 3 aims to cut greenhouse gas emissions from U.S. power stations by nearly a third by 2030, mainly by pushing them to change from coal to natural gas. Power stations are the largest single source of U.S. greenhouse emissions, accounting for about a third of the total.
The Clean Power Plan could run into strong political opposition from the coal industry and some Republican presidential candidates have already criticized it as damaging for the economy. But by announcing it now, the Obama administration is clearly signaling ahead of the Paris conference that it expects the rest of the world to also be serious about curbing emissions.
The European Union
Taken together, the 28 member states of the EU are the third largest contributor to global pollution -- 9.6 percent of the world's total CO2 emissions. The states that contribute the most are those with the biggest economies: Germany, France, and Italy.
The EU has said in planning for the Paris meeting that it will cut at least 40 percent of its emissions by 2030 compared to 1990.
"I now call on all our partners, especially major and emerging economies, to come forward in time and at least match our level of ambition," said the EU's climate commissioner, Miguel Arias Canete, when Brussels adopted its plan in March. However, that may be easier said than realized.
India is the world's No. 4 biggest emitter, putting out 6.7 percent of the world total.
New Delhi has so far resisted calls to set ambitious reduction targets and has yet to file its plans ahead of the Paris summit. Arguing that it has still to pull millions of its citizens out of poverty, it has ruled out setting a date for when its emissions would peak -- as China has -- and instead is expected to come forward with a two-pronged strategy. One would be to set goals it could reach using only its own domestic financial resources, the other is to set goals it could reach with aid from the developed world.
The same two-pronged strategy is favored by many other developing countries which have already submitted their plans ahead of the Paris summit.
"A lot of poorer or developing countries have submitted proposals which say we can do so much with our current levels of funding but we can do a little bit more if you offer us some extra cash," says King. "I think the critical caveat in a lot of these will be that you need to come up with the cash to help us do this, otherwise we cannot."
The No. 5 place for global greenhouse emissions is held by Russia, with 5 percent of the world total.
Moscow has announced ahead of the Paris meeting that it could cut its emissions by up to 30 percent by 2030 compared to 1990 levels. Yet it also has said that the level of its cuts would depend on how ambitious the other players are ready to be.
However, as with many other countries, there are uncertainties regarding how Russia calculated its emissions when it submitted its plans. That is because it has enormous tracts of forest, and nations routinely count the amount of CO2 that their "forest sinks" can absorb from the atmosphere as an offset to part of the total industrial emissions they produce.
"Countries are making submissions basing their emissions trajectory on how much their forests are supposed to soak up over the next 10, 15, 20 years," notes King. "I think there is a tremendous amount of uncertainty about who is going to monitor these forests, to ensure that these are properly maintained and are not used for other industrial purposes. And how are they being calculated, what counts as a forest sink, is it forest, is it a piece of farmland, is it a piece of peat land?"
Still, proponents of curbing global greenhouse emissions say that there is one widely-agreed baseline that gives all players an impetus to look for solutions, despite their many different approaches.
That is a shared desire to keep the rise in global temperatures associated with climate change and industrial emissions to below 2 degrees Centigrade -- the level beyond which scientists warn of increased frequency of extreme weather events and accelerated melting of polar ice. Nations attending the climate change summit in Cancun in 2010 agreed to keep global warming below that "speed limit" and it remains the goal today.