25 Aug 2017

Climate change, what change?

Calima over El Pinar yesterday afternoon. You can't even see the forest-covered mountains behind the village in the middle of the picture.

If Donald Trump had been living on El Hierro, we could forgive his denial of climate change. Sitting in a huge deep tub of cool water – remember the Cold Canary Current? – and fanned by the Trade Winds, you can’t expect us to feel average changes of less than 0.5ºC in temperature year after year. That’s what the meteorological institute, infallible in hindsight, tells us has been happening. But this year we know something has happened. What I describe is the something in El Pinar where I live. If you want a general idea of the island, compensate for our altitude and orientation, i.e. take off a few degrees in summer and add a few in winter, reduce insolation by 30% and increase humidity a little.

Let’s start with the temperature. Over the years we have noticed a general tendency towards longer, but not necessarily colder, winters and shorter, hotter, summers and more heatwaves – this year we’re in our fourth or fifth. In any case, where I live it used to go up to 35ºC only on three or four days each summer. This August it has hovered around or above that every day.

Malmsey (Malvasia) grapes. These would normally be ready for
harvesting about now, but temperature, low humidity and insolation
have dried the bunches before they ripened. Some vines have
lost their leaves and on many the grapes are simply mummified.
At 850 metres above sea level, we have noticeably less muck in the air above us, and being almost in the tropics the sun is right overhead. So our insolation is at best something to be reckoned with. This year it is brutal. Yesterday morning I experimented with my digital thermometer: the air temperature in the shade was 30ºC, after ten minutes’ exposure to the sun the probe read 57ºC and after 20 minutes it read 64ºC. NO SUNBATHING!

Talking of muck in the air, we used to have ‘calima’ – airborne dust from the Sahara – during summer. Nowadays it appears any time of the year.

Very strong winds are less frequent. Fifteen years ago one blew away our greenhouse and snapped the trunk of our largest apricot tree. Although we still have north and northwesterly winds they are not nearly so strong.

Five years ago, in winter at least once or twice a week we had a dehumidifier on for a few hours in our bedroom. Since January this year the relative humidity has rarely gone above 40% and has often been below 20%. I wake up every morning with a tongue like old leather and hair like Rod Stewart. Although relative humidity should ideally be around 60-70%, here it is normally between 50 and 65%, a bit lower at the height of summer.

Perhaps the most important item in our climate equation is rainfall. As we have grapevines and fruit trees, growing years are more relevant and so our figure for the first year shown, ‘2009’ really means ‘October 2008 to September 2009’. Our average rainfall of 477 mm/yr is quite high for the Canaries but the total each year is very erratic, from 100 mm to 730 mm – or litres /square metre – and most of that falls heavily on a few odd days, generally in November and March. Between March and November we have drought. I can find no pattern or correlation in the annual rainfall figures, except certain coincidence with the North Atlantic Oscillation (NAO) sending us areas of low pressure, westerly winds and rain, or withholding them.

Annual rainfall from October to September, starting October 2008.
Figures reflect the rainfall measured at Manacen, El Pinar.

So if you take all these factors (I’m sure there are more but these are quite enough), put them in a box and shake energetically, you get this year’s, or that year’s, weather. It seems for our agricultural year 2016-2017 only the worst factors came into play: our throats are parched, the trees are almost leafless, the grape harvest is in tatters, our gardens are withered and we can’t go outside between twelve and five. For the first time in my life I wish it were winter instead of summer! Perhaps the year 2017-2018 will be a hand of aces. And maybe Climate Change will give us a more obliging old NAO year after year and our island will become the eden it deserves to be. Anyway I don’t think we want DT to come to find out!