When atmospheric CO2 concentrations go up, we all can agree that global mean temperature will go up. We might debate why CO2 concentrations are changing, and we also might wonder how this will might matter for things living on this planet. One clear answer: the crop we grow will be give us less nutrition.

Plant physiologists have known for a long time that plants generally grow much better high-CO2 environments, getting taller and reproducing eariler. CO2 is the basic ingredient of all plant material, thanks to the magic of photosynthesis. But in these enriched environments, plants are just adding carbon (the C) without adding much else — like nitrogen (N). So the ratio of C to N goes way, way up. For food, we care a lot more about the N than the C, since that’s the protein we’re looking for.

That’s the general notion. But it’s really just a hypothesis about how things might work — where’s the evidence? Three scientists in Texas have just now put together all the individual studies looking for answers to these questions, and find a powerful, consistent pattern of reduced protein in the edible bits of all crops which have been tested. That goes for kernals of corn, ears of barle, and grains of rice. Read all about it here.

So: if you ever hear some punditry about how more CO2 is actually good for agriculture, now you’ll be prepared!