The April 9 front-page article “Earlier blooms give flower lovers a chill” nicely summarized the worldwide evidence for season creep, the increasing length of the growing season. It’s important to emphasize that plants, by the nature of their metabolism, grow in response to the average temperature around them — in other words, they integrate the ups and downs of temperature. Plants, through season creep, are telling us that the average temperature is increasing — a strong piece of evidence for global warming. But are we listening?

The article focused on blooms, but the impact of warming on agricultural crops is of critical importance to worldwide economies. To meet the nutritional needs of growing populations, world agriculture will have to increase yields substantially. But even with longer growing seasons, the worldwide food supply is at risk because higher summer temperatures adversely affect crops such as wheat that are vulnerable to hot and dry weather.

The striking evidence of the temperature sensitivities of plant metabolism is prompting new studies about more temperature-resistant crops. The results from these studies will help the world adjust and adapt to the climate change that is rapidly coming upon us.

D. James Baker, Washington

The writer is director of the Global Carbon Measurement Program at the William J. Clinton Foundation and a former administrator at the National Oceanic and Atmospheric Administration.