Last week, Senate Republicans moved to undermine the impending climate talks in Paris by vowing to block the $3 billion President Obama had pledged to help developing nations prepare for the impacts of climate change.

The financial aspects of fighting climate change have always been complex, to say the least. At the 2009 climate summit in Copenhagen, trust broke down between developed and developing countries, and the talks failed to lead to a significant reduction in greenhouse gas emissions. However, then-Secretary of State Hillary Clinton was able to salvage hope from the jaws of discord. Clinton paved the road for a quorum on climate by promising the United States would help amass $100 billion a year by 2020 to aid developing countries.

The $100 billion in climate financing will prove essential to building trust between developed and developing nations. It’s part of the reason why December’s climate summit in Paris, the long-awaited sequel to Copenhagen, will succeed where previous efforts have failed.

If countries are to limit warming to 2 degrees C above industrial levels — their stated goal — developing nations will need to move away from fossil fuels, even as their economies expand and their energy needs increase. The $100 billion will help poor countries fund renewable energy projects where coal or other dirty fuels make for a cheaper alternative.

This money will also be used to aid vulnerable nations — particularly those in South Asia and Sub-Saharan Africa — to prepare for the worst of climate change. These regions have historically contributed the least to global warming, and yet they stand in the bull’s eye for drought, heat waves, severe storms and coastal flooding. The first eight Green Climate Fund projects were just approved.

According to some experts, what’s notable about the $100 billion in climate finance not how much it amounts to, but how little.

“In a $100 trillion world economy, $100 billion — one-thousandth of that or 0.1 percent — you know, it’s really affordable,” said Jeffrey Sachs, Director of the Earth Institute at Columbia University. “When you look at numbers, you say, ‘Not only is this affordable, it’s a must, because we can’t afford to fail,’” he added.

When you look at numbers, you say, ‘Not only is this affordable, it’s a must, because we can’t afford to fail.’”

To put the $100 billion of climate finance in perspective, Superstorm Sandy inflicted roughly $50 billion in damage, and that’s just in the United States. One storm. One country. One time. The $100 billion in annual climate financing — just twice the losses of a single storm — will support vulnerable nations across the globe as they cope with climate change and make the inevitable transition to clean energy.

Notably, extreme weather poses a major stumbling block to growth. Severe storms thrash critical infrastructure like roads, bridges and power lines. Drought impedes agriculture. Heat saps productivity.

“I’d say it’s a fantasy to think that you can fight poverty and not fight climate change because that poor are going to be in the first line of vulnerability just about anywhere in the world,” Sachs said. A mild climate is essential to development. Reining in global warming will clear the path for emerging economies.

In a statement issued in September, Secretary of State John Kerry said that developed countries “are well on [their] way to achieving this $100 billion goal.” By some estimates, the financing is halfway there, with the final pot likely involving a mix of public and private money. While Republican lawmakers have blocked U.S. contributions to climate financing thus far, Secretary Kerry told the Financial Times, “We’ll get there, because the trade-offs of the budget are such that when something is a high enough priority for a president, you have a way of getting it done, even though it’s opposed by people.”

As Sachs explained, climate financing forms a key part of what developed countries can and should do on climate change, along with limiting pollution and investing in research. The $100 billion is, for wealthy nations, a down payment on a safe climate, a show of good faith that will bring developing nations to the table, ensuring that emerging economies like Brazil and India promise not to soil the global commons. Numerous studies have demonstrated repeatedly: the cost of inaction far outweighs the cost of action. Climate financing is an investment — $100 billion towards the enduring safety and security of all nations, both rich and poor.

Jeremy Deaton writes for Nexus Media, a syndicated news service covering climate, energy, policy, art and culture. You can follow him @deaton_jeremy.