Food prices rose 0.4 percent in the United States last month, according to the Bureau of Labor Statistics, thanks in large part to ongoing drought in the Western U.S. and other parts of the world. Earlier this month, atmospheric carbon dioxide rose over 400 parts-per-million earlier in the year than at any previous recorded time. Those things are only loosely linked right now. That link is growing stronger.

Change in CPI food prices, via the Federal Reserve

The Wall Street Journal links the food price increase to "tight cattle supplies after years of drought in states such as Texas and California" — as well as increased demand for milk. It's also thanks to higher prices for fruits and vegetables, such as are produced in California, and coffee prices, which are up thanks to drought in Brazil. The Department of Agriculture estimates a 2.5 to 3.5 percent increase in food prices over the course of 2014. That's lower than other recent years, but the spike from January to February — seen at right — is clear.

Whether or not California's drought is a direct result of climate change is debated by scientists, as was the extended, historic drought in Texas. But extended droughts in dry areas are precisely what you'd expect to see as climate change accelerates. The UN's Intergovernmental Panel on Climate Change explains how precipitation patterns will change as the world warms: more rain in wet areas, more drought in dry areas, both in some places.

Even if climate change isn't the sole reason for California's drought, which was broadly expected to lead to an increase in food prices, climate change certainly exacerbated it. The New York Times explained in February: "[W]hatever the cause, the effects appear to have been made worse by climatic warming. And in making that case last week, scientists said, the administration was on solid ground."

The unrestrained release of greenhouse gasses like carbon dioxide into the atmosphere are assuring that the world will keep seeing the effects of climate change. At Mauna Loa Observatory in Hawaii, which has been tracking the atmosphere's carbon dioxide for decades, levels topped the symbolic 400 ppm last week. Usually CO2 peaks in May, declining during the summer when photosynthesis is at its height. Reaching the 400 ppm mark this early is unprecedented. It's two months earlier than the mark was hit in 2013.

Ralph Keeling, for whom graphs of CO2 concentrations are named, responded to the data. "Probably we’ll see values dwelling over 400 in April and May," he said. "It’s just a matter of time before it stays over 400 forever."

Meaning that the current climate we're experiencing is the best of what the immediate future holds: the most temperate, the most stable. So the growth cycles in Brazil, Texas, and California — and in the Midwest, which is already seeing its corn-growing region moving further north — will continue to shift, disrupting how we grow our food. The link between 400 ppm and 0.4 percent is circuitous. But it exists. And both those numbers are likely to continue to increase.