Countdown to caucuses: Democrats offer subtle differences in environmental policy

Iowa Democrats regularly list the environment as one of their top voting issues.

But finding daylight among the presidential candidates' environmental policies can be challenging. It's not uncommon to hear a candidate talk about a 'Green New Deal,” but the details of those policies vary by candidate.

Most of the Democratic presidential candidates have said they would use executive authority to put the U.S. back into the international pact for countries to address climate change known as the Paris Climate Agreement. They support myriad renewable energy programs and initiatives, including a robust federal ethanol mandate, a favorite program in Iowa.

The differences, indeed, are subtle.

For example, many of the candidates say the U.S. should set a goal of net-zero carbon emissions: balancing the amount of carbon dioxide humans put into the planet's atmosphere with corresponding greenhouse gas reductions.

But there is a subtle difference in the candidates' timelines: Bernie Sanders and Joe Biden say the goal can be achieved by 2050, while Elizabeth Warren sets a more aggressive timeline of 2030.

Some candidates, like Pete Buttigieg, have expressed support for a carbon tax - an additional tax on businesses that burn carbon-based fuels like coal, gas and oil.

Bernie Sanders, as another example, has called for raising taxes on polluters without specifically calling it a carbon tax.

Many of the candidates also pledge to reduce tax subsidies for carbon-based fuel industries.

Tom Steyer has pledged to make climate policy his No. 1 priority. The California businessman in 2013 started a national advocacy group for climate-friendly policy, and said as president he would on Day 1 declare climate change a national emergency.

Iowa farmers may be interested to hear the candidates' positions on carbon sequestration: removing carbon dioxide from the atmosphere and storing it in the soil. Buttigieg and Sanders, for example, support paying or offering incentives to farmers who engage in the practice.

Joe Biden

' Beginning on the first day of his presidency, Biden vows to sign a series of executive orders to ensure a 100% clean energy economy and net-zero emissions no later than 2050.

' Put the United States back into the Paris Climate Agreement.

' Support the Green New Deal.

' Invest in a clean energy future and environmental justice, paid for by rolling back the Trump tax incentives for corporations.

Pete Buttigieg

' Net-zero emissions by 2050

' Economy-wide tax on carbon emissions.

' Create a $250 billion 'American Clean Energy Bank” to fund local clean energy projects

' 10-year, $250 billion 'Global Investment Initiative” to spur development and specifically to counter China's Belt and Road initiative, which intends to deliver trillions in infrastructure financing to Asia, Europe and Africa.

' 10-year, $200 billion fund for the 'training and transition” of displaced workers.

' Convene 'Pittsburgh Climate Summit” in his first 100 days in office so cities across the U.S. and world can share best practices.

Amy Klobuchar

' Klobuchar is a co-sponsor of the Green New Deal and pledges to put the United States back in the Paris Climate Agreement her first day as president.

' Bring back the gas mileage standards.

' Hold the fossil fuel industry accountable by ending federal tax subsidies to companies for oil exploration and production.

' Bring back the Clean Power Plan and negotiate stronger emission standards for states.

' Keep carbon emissions in check by imposing a carbon tax on companies based on their output of carbon dioxide.

' Invest in clean-energy jobs and infrastructure, provide incentives for tougher building codes and promote rural renewable energy.

Bernie Sanders

' Sanders supports the Green New Deal. He vows to transform the energy system to 100 percent renewable energy and create 20 million jobs to solve the climate crisis.

' Invest in weatherization, public transportation, infrastructure and high-speed broadband.

' Reduce emissions throughout the world, including providing $200 billion to the Green Climate Fund and rejoining the Paris Climate Agreement.

' Invest in conservation and public lands to heal soils, forests and prairie lands.

Elizabeth Warren

' Warren is a co-sponsor of the Green New Deal legislation in the Senate.

' Net-zero emissions by 2030.

' 'Open to” but does not plan for carbon tax.

' Establish a 'Green Bank” to mobilize $1 trillion in infrastructure investments over 30 years.

' Boost fund from $1 billion to $15 billion for the Conservation Stewardship Program to encourage farmers to help fight climate change.

' 'Green Manufacturing Jobs”: a $400 billion investment over 10 years in clean energy research and development; a $1.5 trillion federal procurement commitment over 10 years to buy American-made energy products; and a 'Green Marshall Plan” in which a new federal office would be dedicated to selling American energy technologies abroad.