Ahead of key hearings about the American Clean Energy and Security Act scheduled for next week, Henry Waxman, Chairman of the House Energy and Commerce Committee, said he will not shift from his proposal to reduce greenhouse gases 20 percent by 2020.

Waxman’s 2020 proposal aims to reduce greenhouse gas levels to those of 2005. It is a more aggressive proposal than U.S. President Barack Obama’s push for a 14 percent reduction.

I want to keep those caps in place, Waxman told Bloomberg TV in an interview airing this weekend, adding that this is what scientists are telling us we must do in order to stave off a global catastrophe.

The bill on its core, proposes a cap-and-trade system that sets the limit of carbon dioxide and other heat-trapping emissions which a car, power plant or factory can emit. It also intends to establish national standards for renewable energy and energy efficiency.

Critics of the bill sustain that it will damage the economy by increasing energy costs.

Starting on Tuesday, a series of four hearings will be held. Waxman expects the climate bill to clear the House before August.