— -- In his announcement Thursday that the U.S. will leave the Paris Agreement, President Trump described the temperature difference estimated as a result of the deal as "tiny."
But tiny numbers have a significant long term impact when it comes to the climate, many experts say. A half-degree temperature difference can lead to consequences like rising sea levels that threaten coastal cities, longer heat waves and could kill off tropical coral reefs, according to research from the European Geosciences Union.
It's difficult to say for sure how Trump's decision to pull the U.S. out of the Paris Agreement will impact the climate but several scientific groups have published projections. Most of those projections predict that even if every other country in the agreement meets their goals to reduce greenhouse gas emissions the global temperature will still rise because the U.S. is one of the top sources of gases that contribute to global warming.
The non-profit group Climate Interactive projects average temperatures would warm an additional 0.5 degrees Fahrenheit by 2100 if U.S. emissions continue as they are now and every other country fulfills their pledge under the deal.
Another scientific group, Climate Action Tracker, puts the impact of additional warming at 0.18 to 0.36 degrees Fahrenheit.
The Sierra Club has also put out numbers that say 60 percent of the emissions reduction goals the U.S. set under the Paris deal could be met by local initiatives – states and cities taking matters into their own hands -- but that analysis assumes that the U.S. completely replaces coal with clean energy.
Another factor that complicates these estimates is that the president has signed executive orders to roll back environmental protections and directed the Environmental Protection Agency to eliminate regulations. The analysis published by Climate Action Tracker found that the U.S. would likely miss its targets under the Paris deal anyway based on Trump's executive orders. Obama administration initiatives like the Clean Power Plan were factored in to discussions about how the U.S. would reduce global emissions, which makes the impact of eliminating those policies and leaving the Paris deal even more unclear.