The main points of the US climate bill

US senators on Wednesday introduced long-awaited legislation to curb carbon emissions blamed for global warming, a key priority for President Barack Obama.

Here are some of the main points of the "American Power Act" authored by Senators John Kerry, a Democrat from Massachusetts, and Joe Lieberman, an independent from Connecticut:

- GOALS

The bill seeks to reduce carbon emissions by 17 percent by 2020 compared with 2005 levels. Further cuts would eliminate 42 percent of emissions by 2030 and 83 percent by 2050.

The figure is in line with a House of Representatives bill approved last year and President Barack Obama's position in international negotiations. The short-term target is modest compared with commitments by the European Union and proposals by Japan, but becomes more ambitious after the plan kicks in.

- EMISSION RIGHTS

The bill is largely based on a "cap-and-trade" system, which restricts the amount of carbon that businesses can emit but lets them trade credits, giving an economic incentive to go green. Cap-and-trade is the basis of European climate policy.

The bill would set up a national system putting restrictions on carbon, abolishing cap-and-trade plans already set up by individual states such as California. But it would compensate states for any lost revenue.

The plan would set the price at carbon initially between 12 and 25 dollars per ton and increase the amount each year at five percent plus any adjustment for inflation.

- PROTECTIONS FOR CONSUMERS, BUSINESSES, FARMERS

The bill promises that two-thirds of revenue from the plan would be sent back to consumers with some funds used to pare the budget deficit. The amount for consumers would rise to 100 percent after the transition.

Mindful of the troubled economy, the proposal puts the burden on major factories and power plants. It imposes no requirements on manufacturers until 2016 and exempts farmers entirely.

- TRANSPORTATION, ENERGY INVESTMENT

The bill promises six billion dollars a year to make the US transportation system more energy efficient along with tax incentives for trucks and other heavy vehicles to shift to clean natural gas.

It also promises broad investment to develop green technology including two billion dollars a year to develop "clean coal," meeting a concern from mining states.

- OFFSHORE DRILLING

The bill would allow offshore drilling for oil but allow states to opt out for projects within 75 miles (120 miles) of their coast, up from just a few miles now.

- NUCLEAR POWER

The bill includes a number of incentives to promote nuclear power, including 54 billion dollars in loan guarantees for the domestic production of nuclear parts.

- INTERNATIONAL DIPLOMACY

The bill warns that if no new global treaty emerges on climate change, the United States will impose tariffs on products from countries that do not curb carbon emissions.

The bill pledges continued US support for developing nations to adapt to climate change, without establishing a new financial figure.