Last week I read an academic paper on this subject and while admittedly not understanding it all, I did get that the wine industry is imperiled. I then proceded to search for related articles and came up with several. All seem to have sprung from the same academic spadework with the key target date of 2050 appearing in each. By that date it is imagined the industry will have changed dramatically to survive in the expected hotter climate.
Carbon in the atmosphere has been measured since the mid 1950s and average world temperatures have now been calibrated backward millions of years. In the current era the globe has warmed 3-4.5 degrees in the last fifty years which contrasts dramatically with earlier centuries in which temperatures fluctuated by as little as a degree or two. For the wine industry the recent warming has actually been good for viticulture. It has meant a longer growing season which in turn means a more consistent harvest. Production has been fine through the decades also although 2012 was off a bit.
Heat hastens ripening, producing more sugars (alcohol) and bolder flavors. Coincidentally the current popular style in wine appreciation includes robust, overly ripe, fruity, high alcohol wines. Knowing the power of advertising and the ability of this industry to woo its base, this may be more of a case of us convincingly offering what we have as the style du jour.
"Heat spikes" are days when the vineyard temperatures reach 95 degrees. Those extreme temperature days have increased in recent years causing concern (and expense) for the industry. Wine grapes prefer to live in the 55-68 degree range and need to be frost free at the other extreme. Life is best for grapes when it is lived in the middle of the extremities.