The best market-based way to…

The best market-based way to reduce greenhouse gases is a price on carbon, either a direct tax or a cap-and-trade system. In both cases, the government can return the income it earns to the people, so it is not a “tax grab”. And the whole point is for businesses and individuals to take steps to reduce their carbon emissions so they don’t have to pay it.
Ontario's Cap and Trade system, linked with Quebec and California, has brought about $3 billion into our province in its first 1 1/2 years and was paying for actions that further reduce greenhouse gas emissions - like upgrades to buildings, rebates for electric cars, and incentives for innovation.
Eliminating the Cap & Trade program has already had a negative impact on the economy in the form of the loss of local contractor jobs supported by home energy retrofit programs.
Most of Ontario’s carbon emissions come from buildings (particularly how we heat them), and transportation. We must reduce these to reach our current emissions target of 30% below 2010 levels by 2030.
Canadians produce about 20 tons of greenhouses gases per person per year, compared to about 9.2 tonnes per person in Norway (another northern country), 6.9 tonnes per person in Europe on average, 7.7 tonnes per person in China, and 1.9 tonnes per person in India.
A recent scientific study (reported here in The Guardian) says that we must stop burning fossil fuels within 10 to 20 years to avoid runaway climate change that may destroy all life on Earth.
On the up side, another recent paper (reported here in Huffington Post) says that if humanity dramatically reduces greenhouse gases within the next 3 years, the resulting “grand economic transformation could bring a $26 trillion economic windfall, create 65 million new jobs, and avoid 700,000 early deaths linked to air pollution.” We in Ontario should be leading the way towards these economic benefits, not dragging our heels and being left in the dust.