The growing season temperature in south-east and south-central UK is increasingly similar to that of the Champagne region in 1961-1990. But wine yield has varied considerably, which can be explained in part by air frost and precipitation at key phenological stages, say the researchers.
Popular varieties such as Chardonnay and Pinot Noir are particularly susceptible to climate variability.
If the UK wine industry is to be a success, wine makers will need the right management strategies and the ability to cope with lower yielding years, suggest the researchers. Meanwhile, further investigation into future climate conditions will help assess risk.
A growing industry
Wine grapes are generally grown in narrow latitudinal bands (30–50° N and 30–40° S), with local conditions an important factor.
But recent research has suggested that, under future climate change, higher latitude regions may have increasing suitability for viticulture, including the UK.
Production of English wine has doubled in the last five years, with sales reaching a record £100m ($141m) in 2015. Most vineyards are located in southern England, in counties such as Kent and Surrey.
There are targets to increase the area of planted vineyards from 2,000 hectares to 3,000 hectares by 2020. Production would increase from 5m bottles a year to 10m bottles.
The UK government has also pledged a tenfold increase in wine exports by 2020.
The researchers from the University of East Anglia and Brock University in Canada studied the main grape-growing regions in the UK and investigated the relation between temperature, rainfall, extreme weather and yield, as well as surveying the views of English wine producers.
Where is wine grown?
Recent vineyard plantings have predominantly occurred in southern England (latitude 50–52° N).
A number of vineyards are found in the south-east (East and West Sussex, Kent and Surrey) and south-central England (Berkshire, Hampshire, the Isle of Wight and Wiltshire).
The data can help reveal the opportunities and threats to the English wine industry.
Frosts in May, rain in June
The UK has been warming faster than the global average since 1960, said Alistair Nesbitt, lead researcher.
The average southern England growing season temperature has consistently been above 13°c since 1993, and since 1989 there have been 10 years where the temperature was 14°c or higher (up to 2013).
To put this into context, this is around the same temperature as the sparkling wine producing region in Champagne from 1961-1990.
But UK wine yields are much lower than that of Champagne: around 2,100 liters per hectare on average compared to 10,000 in Champagne.
“We found that while average temperatures over the growing season have been above a key minimum threshold for ‘cool-climate’ viticulture for two decades, wine yields [in the UK] vary considerably,” said Nesbitt.
Weather variations and extreme events impact productivity from year to year, says the study. For example, frosts pose a particular threat to yields if they occur at critical times such as straight after bud-burst in spring.
The researchers found that spring months (April and May) have become warmer in the last 25 years. This is significant because it is when buds burst and initial shoot growth occurs, and so warmer temperatures indicate an earlier and longer season.
But warmer April temperatures lead to potential for increased vulnerability if a May air frost follows.
Wet weather in June, particularly with cool and overcast conditions, can delay flowering and reduce the number of berries and young grapes on vines. Researchers saw a correlation between high June rainfall and poor yield.
Sensitivity of Chardonnay and Pinot Noir
The popularity of Chardonnay and Pinot Noir puts the sector at greater risk as well, say the researchers.
“Critically, the drive to produce English sparkling wine has led to a significant change in dominant cultivars grown. Chardonnay and Pinot Noir are considered more ‘marginal’ cultivars than those they have replaced and are possibly more affected by poor weather conditions,” says the study.
“It is perhaps their greater sensitivity to the UK’s cool climate conditions that is reflected in a closer relationship, post 2004, between yield and growing season average temperature. The conclusion is that English sparkling wine production has risen, but as a result, the sector is now at greater risk from variability in average growing season conditions.”
More climate projections needed
The researchers conclude: “We have shown that UK yield still faces regular threats from unfavorable weather at key points in the calendar. Viticultural opportunities can be realized in years where these threats do not materialize.
“Viticulture in the UK is vulnerable to weather variability resulting from the UK’s geographical positioning, a vulnerability recognized by producers. For those investing in UK, viticulture climatic risks may be ameliorated through management strategies, market forces and their ability to cope with lower yielding years. Projections for future climate conditions in the UK will support future risk analysis.”
Source: Australian Journal of Grape and Wine Research. Published April 1, 2016.
Title: ‘Climate and weather impacts on UK viticulture’
Authors: A. Nesbitt, B. Kemp, C. Steele, A. Lovett, S. Dorling.