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Nowadays, meteorologists with computers track changes in climate. Winemakers got there first. Centuries ago, monks tending vineyards filled books with details of harvest dates, and a recent paper in the journal Nature Climate Change says those records can tell us something about global warming. NPR's Allison Aubrey reports.
ALLISON AUBREY, BYLINE: Wine grapes are pretty sensitive to temperature and droughts. And during hot years, winemakers tend to harvest their grapes earlier. Elizabeth Wolkovich, who runs an ecology lab at Harvard University's Arnold Arboretum, thought early records of harvests could be useful.
ELIZABETH WOLKOVICH: I think grapes are a great window into changes in climate. So my colleague, Benjamin Cook of NASA, and I were interested in using long-term harvest dates of wine grapes to see how climate had changed and even to try to reconstruct climate.
AUBREY: Wolkovich says the further you go back in time, the less information we have about climate.
WOLKOVICH: We often don't have the really long-term records that we want to be able to say were things happening in the 1700s and 1800s the same as what's been happening in the 1900s and onward?
AUBREY: But with grapes in France, Wolkovitch's colleagues found records going back to the 1300s. Monasteries weren't just for prayer and contemplation. Monks tended large vineyards and kept meticulous records. Wolkovich's colleague, Inaki Garcia de Cortazar Atauri, tracked down these records.
WOLKOVICH: Inaki went to the old libraries in Avignon and pulled down the books that were kept by different sort of church properties. And these handwritten records were carefully compiled from all across France.
AUBREY: When they put all of this data together, they saw a pattern in Western Europe that remained stable for centuries. It took a heat wave and a drought in the same year to drive temperatures high enough to lead to an early harvest. But beginning in the 1980s, this pattern started to break down. Rising temperatures alone started to move the harvest forward. And this trend has accelerated.
WOLKOVICH: So if you think about places in the south of France where they're tending to harvest usually in late September, early October, they're shifting earlier across France about two weeks. So a really big change in when we harvest wine grapes.
AUBREY: Now, if you're a wine lover, this is not necessarily a bad thing, at least in the short term.
WOLKOVICH: Hotter summers are usually higher-quality wines in France. And so we do actually have higher-quality wines on average with climate change. The issue is we can't keep warming up the system and expect that to continue.
AUBREY: And it's not just in Western Europe that weather conditions are forcing winemakers to think about how to adapt to the changes. Lee Hannah is an ecologist with Conservation International. He says vintners around the globe are buying up land in places that used to be considered too cool for winegrowing.
LEE HANNAH: Places like Tasmania, even in Montana where people are starting to grow wine grapes. And the crop model suggests that those areas will become really good for growing wine.
AUBREY: But don't expect a lot of Montana merlot. Vintners there are experimenting with hybrid grapes that are more suited to their climate. Allison Aubrey, NPR News. Transcript provided by NPR, Copyright NPR.