Climate change drove weeks of crop-withering temperatures last year in the West African countries that underpin the world's chocolate supply, hitting harvests and likely further stoking record prices, researchers said Wednesday.

Farmers in the region – which account for some 70% of global cacao production – have struggled with heat, disease, and unusual rainfall in recent years.

That has caused an explosion in the price of cocoa, which is produced from the beans of the cacao tree and is the main ingredient in chocolate.

A new report found that "climate change, due primarily to burning oil, coal, and methane gas, is causing hotter temperatures to become more frequent" in Ivory Coast, Ghana, Cameroon, and Nigeria.

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The study, by the independent research group Climate Central, found the trend was particularly marked in Ivory Coast and Ghana, the two biggest cacao producers.

Using observational data from 44 cacao-producing areas in West Africa and computer models, the researchers compared today's temperatures with a counterfactual of a world without the effects of climate change.

They looked at the likelihood of these regions facing temperatures in excess of 32 degrees Celsius (89.6 Fahrenheit) – above levels considered optimum for cacao trees.

The report calculated that over the last decade, climate change had added an extra three weeks of above 32C heat in Ivory Coast and Ghana during the main growing season between October and March.

Last year, the hottest year globally on record, they found that climate change drove temperatures above 32C on at least 42 days across two-thirds of the areas analyzed.

Researchers said that "excessive heat can contribute to a reduction in the quantity and quality of the harvest."

Many other factors were also potentially harming cacao trees and boosting prices, they noted, including mealybug infestations, rainfall patterns, smuggling, and illegal mining.