In the run-up to the upcoming Paris Climate talks, world leaders are realizing the stark nature of climate change. The contribution of fossil fuel pollution to global warming is high on the agenda, but observers wonder if action will be forthcoming to meet the serious challenges.

Scientists say that further warming above two degrees Celsius could be catastrophic, according to Agence France-Presse.  Nations at previous climate meetings have agreed to meet that target, but a comprehensive action plan towards the goal is still undetermined.

Instead, 150 countries have outlined carbon cutting measures that fall short of the goal, leaving likely warming at three degrees Celsius. In a report earlier this year, the Executive Director of the executive director of the International Energy Agency noted that the cost and challenges of addressing climate change grow increasingly complex the longer countries wait to take them on.

Exeprts say that the most cost effective strategy for getting the number down is to quickly transition from fossil fuels to non-polluting renewable energy sources. With the economics of renewable energy sources such as wind, solar, and water power coming down, such a transition is more feasible than ever.

The United Nations Intergovernmental Panel on Climate Change says that 80 percent of the world’s energy must come from renewable energy by 2050 if the world is to meet the two degree goal.

But governments, including the U.S., still subsidize fossil fuels to the tune of half-a-trillion dollars a year, four times more than they invest in renewable energy. Meanwhile, many developing nations are hoping to skip the problems associated with fossil fuel energy, and are looking instead to boost development through adoption of non-polluting solar and wind resources.

For example, India is investing large resources into renewable energy projects, and is looking to install 175 gigawatts of capacity from renewable sources by 2050.