I think that article is three fifths true, makes two significant lapses, and is written poorly and more alarmist than necessary.
True: the planet is warming.
True: plants suffer a lot in heat and eventually stop photosynthesising (and soon die).
True: we need these plants.
Important lapse 1: the graph of photosynthesis and temperature, a key piece of the article, fails my epistemological tests.
All their other graphs are derived from the article you link to, are well labeled and show the sort of scattered data one expects. The photosynthesis/temperature graph is not well labeled (units for photosynthesis?), is never attributed to a source (and I followed the links to other Kos articles) and IMHO has data points that fit the required curve too damn neatly to be real. The kicker for me, though, is that it does not say which species of plant this is for - different species would have different levels of tolerance. For example, equatorial regions are covered in forests. There might be truth in this, but that graph is IMHO not up to it.
Important lapse 2: Now consider the other graph you have shown. It is
not a forecast of average annual temperature, nor even the highest temperature expected each year. It is the T100. It is well explained here:
http://texasclimate.org/ClimateChang...8/Default.aspx
Quote:
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When assessing the consequences of climate change for human health and most ecosystems, very high temperatures are much more important than average temperatures. Earlier studies have shown that cold extremes will warm faster than warm extremes and that warm extremes will warm faster than average temperatures. European scientists have published a study focused on extremely high air temperatures, represented by the 100-year return temperature (T100). (T100 is a specific statistical expression that means that every year you have a 1% chance of getting that temperature.) Their results show a projected global-mean temperature increase of 3.5°K by 2100, which is at the upper end of the range given by the models analyzed in the 2007 IPCC-AR4. The authors acknowledge that the present generation of climate models, including the one used in this study, tends to overestimate extreme temperature values. However, even after correcting for this bias, they found that by 2090-2100, projected T100 far exceeds 40°C in Southern Europe and the U.S. Midwest and even reaches 50°C in large parts of the area equatorward of 30°, notably in India and the middle East, and also in most of Australia. The projected T100 values, the authors note, should be taken seriously, since they indicate that potential for dangerously high future temperatures in densely populated areas.
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So those temperatures you are looking at on that graph are 99% likely higher than any you would actually experience even once each year.
Poorly written and alarmist? IMHO, yes. It jumps around from photosynthesis to human heatstroke, and throws various examples around in jumbled order, and I believe has misused one respectable graph and used one that is suspect.
That said, cereal crops
are crucial to human civilisation, they
are harmed by heatwaves, heatwaves
are expected to become more common, this
is bad. It's not quite as dire as that article makes it look.