Earth & Sky

CO2 is changing ocean chemistry

JB: This is Earth and Sky. Scientists say there’s more carbon dioxide in our atmosphere now than in the last 400 million years.

DB: And some of that CO2 is going into the oceans. Ocean water takes carbon dioxide from the air and turns it into carbonic acid. Ocean surveys since the 1960s show a shift in ocean chemistry toward increasing acidity. That’s a problem for many ocean organisms – shell-builders such as corals – as well as phytoplankton and snails at the bottom of the ocean food chain.

JB: But some phytoplankton do better with more C02. They need it for photosynthesis. Scott Doney of the Wood’s Hole Oceanographic Institution told us atmospheric CO2 and ocean acidity both have fluctuated over Earth’s long history. There’s evidence that different organisms evolved at different times depending on the chemistry of the ocean. The difference now, he says, is that we’re increasing C02 in the atmosphere at a rate 10 to 100 times faster than at any time known before.

Scott Doney: The kind of change that humans are inducing now – either through changing ocean acidity or though global warming – are so much more rapid than anything that was seen in the geological past that it’s really hard to predict what’s going to happen.

_DB: That’s why, Doney says, scientists can’t predict exactly what will be living in Earth’s oceans of the future. Special thanks to NASA explore, discover, understand. We’re Block and Byrd for Earth and Sky.

CORRECTION: In our program, we mistakenly said that today’s atmospheric carbon dioxide levels are higher than they’ve been for the past 400 million years. We should have said 400 thousand years. The evidence for past carbon dioxide levels come from gas trapped in ice cores. These records do not extend as far back as 400 million years. We regret any confusion this may have caused.