The pessimism among policymakers — who are attending spring meetings of the I.M.F. and World Bank in Washington this week — contrasts with financial markets. Despite a bumpy couple of months, stocks and most other financial assets are still priced at levels that suggest growth will continue apace for some time to come.

“Economists are paid to worry,” said Nathan Sheets, chief economist at PGIM Fixed Income and a former official at the United States Treasury and the Federal Reserve. “We’re paid to find problems and challenges. I think the markets, on the other hand, are pretty good at living in the moment.”

What are these policymakers so worried about? Is this just a bunch of economists living up to their field’s reputation as the dismal science — or worse, letting their own policy preferences shape their forecasts? Or is the world economy, for all its apparent prosperity, actually in peril?

Let’s look at the interrelated threats the economists see.

Trade War Worries

President Trump tweeted last month that trade wars are “good, and easy to win,” but it is safe to say that leading economic policymakers do not agree. They instead see the risk of ruin in the administration’s tariff threats — a cycle of retaliation that could disrupt companies’ supply chains and cause global commerce to falter.

Image Steel coils for car production in Emden, Germany, last month. A steep tariff on steel imports is among the threats from President Trump that have unnerved economists. Credit... David Hecker/Epa-Efe, via Rex, via Shutterstock.

Ms. Lagarde argued in a speech last week that the global trading system has had tremendous benefits in terms of reducing poverty and creating higher-wage jobs. “But that system of rules and shared responsibility is now in danger of being torn apart,” she said.