Wine- the real crisis

This weekend, I woke up to a horrifying message from a friend. This screenshot from mic.com.

In all seriousness, whether or not wine will become more expensive or harder to come by as the effects of climate change begin to be felt is a minor issue (understatement of the century) compared to other predicted effects, particularly those affecting people in the Global South. However, given how widely reported this story has been I thought it would be interesting to check out the science behind it.

The headlines were triggered by the International Organisation of Wine and Vine’s (OIV) latest report. It reports a fall in total production of 5% compared to 2015, making this year’s production among the three worst this century. 

Image 2: Trends in global wine productions using OIV data.

It has been reported in many articles (including in The Guardian, CNN and The Independent) that this is attributable to climate change. In the OIV’s press release they briefly mention that South America was ‘strongly affected by climatic events’. The OIV’s Director General reportedly added “output was greatly affected by exceptional weather conditions. If there is one product that is vulnerable to weather events, it’s wine,” and "with global warming, we're witnessing an increase in exceptional events that are more frequent, longer lasting and of greater scale."

Let’s examine these claims one by one.

Firstly: could ‘climatic events’ really explain the fall in production in South America? The climatic event in question is El Niño, a reversal in usual weather patterns in the South Pacific. It causes dramatic changes in rainfall patterns and temperatures across the Southern hemisphere. This year’s El Niño is one of the most powerful ever recorded and had massive impacts, including droughts in Brazil and floods and landslides further south. It’s pretty much inevitable that destructive climate events of this scale result in overall reductions is agricultural productivity, and grapes are no exception.

It’s also true that climate change is likely to exacerbate these effects. There has been a lot of speculation and debate for a long time about how climate change may affect El Niño events, but a recent study concludes that these events will become stronger and more frequent with climate change.

But what about elsewhere? Much of the decrease in production is indeed attributable to South American countries. For example, production in Brazil decreased by 50%. However many other countries also saw a fall in wine production. The biggest absolute decrease in wine production occurred in France, which accounted for more than a third of the total global decrease.  El Niño mainly affects the South Pacific and neighbouring regions, and although it is true that more local climate events can have knock on impacts around the globe, it is unlikely that El Niño was the sole cause of wine production decreases in Europe.

So could anthropogenic climate change also be affecting wine production? A 2014 review paper published in the journal ‘Wine Economics and Policy’ suggests climate change will affect wine production in a number of ways, including reducing both productivity and the land available for vineyards, requiring changes in grape varieties grown, causing fundamental changes in wine chemistry, and increasing pests and diseases attacking vines. It also corroborates the above statement about the susceptibility of grapes to changes in climate (although given that the paper features the line ‘wine is not essential to human survival’ some may be inclined to reject its findings completely).

Another paper published in Nature Climate Change earlier this year compared past climate records to vineyard records in France and Switzerland. It found that although recent climate change has in fact resulting in some outstanding vintages, the current decoupling of summer heat waves and droughts is likely to negatively impact future wine production. 

It seems that the assertions in these media stories are true. However, as is often the case, the headlines don’t accurately represent the actual stories or the OIV report they’re based on. The OIV’s tiny mention of ‘climatic events’ refer to the most recent El Niño,and the Director General’s follow up comments (rarely even mentioned in media stories) to its interaction with climate change.  Headlines such as ‘Attention wine lovers: You might want to start paying attention to climate change’, while factually correct, don’t accurately reflect the article or the report on which it is based.

Looking at the graph above, it s also clear that this year’s overall production, although genuinely lower than recent averages, is not as low as headlines like ‘Global Wine Production Is Collapsing Thanks To Climate Change’ suggest.

As always then, this story is a reminder to always take media hysteria with a pinch of salt. And if in doubt about the science- send it this way!

The world's biggest hoax? Part 2

This post follows on from last week’s post and aims to answer the question: does evidence support the idea that human activity has played a significant role in this change?

Most people have probably heard the story of CO₂ and the greenhouse effect, but here’s a diagram to recap.



Figure 4: How greenhouse gases like CO₂ cause the Earth to warm.

You may well have seen in the news recently that CO₂ reached a permanent concentration of 400ppm in theatmosphere, which probably means nothing to you until I tell you that’s the highest it’s been for over 800,000 years. The IPCC states that CO₂ is the largest single contributor to increases in temperature between 1750 and 2011.

As is commonly pointed out by sceptics though, CO₂ has many natural sources- so who’s to say us burning fossils fuels is to blame? Well, apart from the fact that we know we’ve burnt enough fossil fuels to contribute that much CO₂ to the atmosphere, CO₂ from fossil fuels has a chemical signal that means it can be identified.

Box 2: The Suess Effect (for those who like chemistry) Carbon has three naturally occurring isotopes: C12, C13 and C14. During photosynthesis, the different carbon isotopes are not absorbed with equal preference, leading to plants and algae being depleted in C13.  As fossils fuels were once live organisms, they too carry this isotopic signal. C14 is also depleted in fossil fuels as it is radioactive. As its half life is close to 5000 years, over the millions of years fossil fuels take to form most has decayed. By monitoring changes in the ratios of different carbon isotopes in the atmosphere we can calculate the contribution of CO₂ from fossil fuels. This was first noted by Hans Suess, and so is named the Suess effect.

It’s not just fossil fuel combustion either- greenhouse gas emissions (22% of the total according to the IPCC) also come from other human activities, such as methane from farming and CO₂ from deforestation.

The above evidence has contributed to the IPCC being able to state that ‘It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in GHG concentrations and other anthropogenic forcings together. The best estimate of the human induced contribution to warming is similar to the observed warming over this period.’

In other words, the very best interpretation of all the very best evidence by the very best collaboration of climate scientists suggests that we are causing the most extreme climate change seen on Earth for thousands, if not millions of years. I can’t argue with that.

The world's biggest hoax? Part 1

In future I’m going to have a look at specific, recent stories about climate change in the media, but I thought I’d write the first proper post here on arguably the biggest question surrounding anthropogenic (human-caused) climate change: is it really happening? This is a big topic so I’m going to split it into two posts.

The arguments against anthropogenic climate change come in several forms. Some deny that climate change is happening:

Snowing in Texas and Louisiana, record setting freezing temperatures throughout the country and beyond. Global warming is an expensive hoax!

— Donald J. Trump (@realDonaldTrump) January 29, 2014

Others, such as more than half the US Senate, recognise that the climate is changing but refute humanity’s role. Many point to past changes in both climate and CO₂ as evidence that current changes are natural or within ‘normal variation’, and deny that there is a scientific consensus regarding our role.

Meanwhile many media outlets regularly publish articles predicting the extreme and imminent effects of climate change, such as destroying infrastructure, worsening extreme weather events and even endangering US military operations. I hope to have a look at some of these in a later blog.

Much has been written for and against these arguments, and I can’t cover the nuances of every point in just one post. I would really recommend the Skeptical Science blog for a more detailed discussion of specific questions (thanks to Anson for the recommendation).

For now though, I will try to answer whether climate change is all a hoax by simplifying it to two key questions:

1) Does evidence support the idea that climate is changing outside the bounds of ‘normal variation’? (This post)
2) Does evidence support the idea that human activity has played a significant role in this change? (Next post)

Firstly, I’d like to share this awesome graphic from NASA. 

Figure 1: Surface temperature changes from 1880 to 2015, using a rolling five year average. Blue colours represent temperatures cooler than the 1951-80 baseline, while red colours represent temperatures above that baseline.

It seems pretty clear that temperatures have risen over the last century-and-a-bit.

Bloomberg plotted NOAA data to show a similar trend. They also highlighted the fact that 15 out of the 16 hottest years on record have been this century, and that 2015 was not only the hottest year on record, but also beat the previous record by a record margin (N.B. NASA’s data suggests the increase from 1997-8 was larger, but corroborates the fact that 2015 was the hottest year on record).

I’d say these data sources are fairly reliable. However, arguably the most reliable sources of data relating to climate change are the IPCC reports. 

Box 1: The IPCC The Intergovernmental Panel on Climate Change is Nobel Prize-winning body, established by the UN to improve understanding of the scientific basis of climate change. It doesn’t carry out its own research, but instead reviews published papers (both peer- reviewed and non peer-reviewed). Based on this evidence, it then reaches conclusions, and, most importantly and interestingly I think, attaches a degree of certainty to these. Although the IPCC has received much criticism in the past, for example over claims about the disappearance of Himalayan glaciers it is generally considered to give a fair reflection of the scientific consensus on climate change. The most recent report, its 5th, was published in 2013.

So what does the IPCC have to say about whether the climate is warming? In the most recent report it states that ‘the globally averaged combined land and ocean surface temperature data... show a warming of 0.85 [0.65 to 1.06]°C²⁰ over the period 1880 to 2012, for which multiple independently produced datasets exist’ (the figures in square brackets are the error margins). 

To me, this all seems fairly conclusive, but let’s look at one of the most popular arguments of climate change sceptics: ‘the great pause’. As the picture below demonstrates, it is a popular claim that temperatures have stopped increasing since the late 1990s.

Figure 2: The Sunday Mail’s headline and graph from October 2012.

As we saw above, warming hasn’t stopped in the last decades. The climate system is complex, and human impacts are modulated by and interact with natural cycles, such as El Niño events (which contributed to the highs in 1997/8 and 2015). We therefore don’t see a totally regular, noise-free pattern, but the short term variation does not negate the long term trend. In fact, a recent Nature paper found that hiatuses like this one are statistically inevitable when such small samples are considered.

However, even if we accept warming is occurring, this is only in the context of 130 years. We know the climate has fluctuated much more wildly in the past, with both ice ages and the sweltering conditions that accompanied the dinosaurs firmly in the public imagination. So why are modern changes any different? The IPCC states with high confidence that ‘1983 to 2012 was very likely the warmest 30-year period of the last 800 years in the Northern Hemisphere’ but this still barely registers on geological time scales. However, if we do look at a longer time scale, such as the Holocene (the last 11,000 years), it is easier to see the significance of recent changes. It is not the magnitude but the rate of warming that is alarming.

Figure 3: Adapted from Marcott et al. 2013 by www.realclimate.org. 

So far, so good (or bad for the inhabitants of planet Earth). But what about our role? Check out my next post to find out!

Fact or fiction- and does matter?

How do you know what you think you know is true? From the current US president Barack Obama stating that ‘no challenge poses a greater threat to our children, our planet, and future generations than climate change’, to current US presidential candidate Donald Trump tweeting that it’s a Chinese hoax. Or from a national newspaper in the UK being criticised by world leading scientists for reporting that ‘appears designed systematically to undermine the credibility of climate science’ to leaked emails from a top British research institute some claim showed they falsified climate science. It can be hard to know what to believe when it comes to climate change.

It’s a topic that’s receiving an increasing amount of attention from scientists, politicians and the general public- and therefore the media. However, mainstream media statements are often made without being fully backed up with evidence, and even when evidence is presented it is frequently misreported or misinterpreted. This has led to a number of ideas about climate change becoming widely accepted despite a lack of support from science. When these issues are contentious, it isn’t helped by the efforts of people who disagree with the scientific consensus, and wish to bring it into disrepute.

With issues like climate change we can't afford to be naive. The best evidence suggests that we need to take dramatic action in the next decade, and that people who are more knowledgeable about the causes of climate change are more concerned and likely to take action. Educating ourselves about climate change is therefore the first step towards finding a solution to this epic challenge. However, even the most sceptical among us don’t have time to fact check everything presented to us by the media and politicians, or even friends, family and colleagues. In this blog I’ll take a look at some current media stories about climate change and what published, peer reviewed scientific papers reveal about their accuracy. So all you have to do is read! I’d love to hear your feedback, so please get in touch with questions, comments or suggestions as to what I should tackle. Thanks for reading, and I hope you enjoy what’s coming up!

Image 1: Probably a myth...