Category Archives: Global Warming

Why deny climate science?

Imagine you are an astronaut who has just returned from the International Space Station and you meet a Flat-Earther… how would you even go about that argument? 

Climate science and evolution are two sciences denied by many. In the case of evolution-denial, a creationist view is faith-based. Those who believe that God made the Universe 6,000 years ago (or equivalent) at least get a religious ‘kick’ out of it. I’m not saying that belief is a good thing (far from it – I think evolutionary science is an incredible human achievement and filled with beauty), but at least I can somewhat understand the mindset that leads to it (or the root of the belief – a religious text).

I cannot say the same for climate science denial. I just don’t understand what motivates it. What is the benefit to the individual? Does it make you feel good to think that all the experts are wrong?

Now, I do what I can to help the environment. I could do much more – I’m aware of the scale of the problem. But I don’t refuel a diesel car or use a petrol lawn-mower and feel riddled with guilt. My scientific opinion on climate change doesn’t follow me around like a dark cloud. I don’t overuse fuel in order to save money, primarily.

When the World Health Organization listed bacon (and other processed meats – of which you probably consume more than you think!) as definitely carcinogenic, I didn’t deny it – I’m not a medical scientist, and I’m sure good science was done in order to reach that conclusion. Equally, when we meteorologists and climate scientists announce that greenhouse gases are causing global warming, I don’t expect non-experts to take issue with that. Whether you act on it is something else, but don’t turn around and say, “Ha! Have you even considered the urban heat island?“. An every-day equivalent would be responding to an F1-trained mechanic informing you that your car needed a new engine by saying “Really? Did you check the oil?”. 

Of course they checked the oil.

In truth, what deniers say to climate scientists is often hurtful, and sometimes very difficult to respond to, purely because of the extent of the misunderstanding – not because we can’t support our science. It’s also plain baffling what some deniers say. When you’re just an excited or concerned scientist doing your thing, experiencing people thowing wild accusations at you is just…bizarre.

So, to all climate scientists – from those currently braving the harsh Antarctic winter, to those dealing with difficult questions from the media, to those who have been sitting coding for two days straight (or more!) – I salute all of you, for everything you deal with.

Going Viral: Some thoughts one week later

Sunday, July 22, 2018, 9:31 PM BST. I put out a relatively simple tweet comprising of two NASA GISS global temperature anomaly graphics – one for June 1976, and one for June 2018. After listening to the media and meteorologists alike comparing and contrasting the current UK heatwave with that of 1976 (something which I had earlier written about here), I felt it necessary to put it into some global context: the planet as a whole is far warmer than it was in 1976 – meaning that regardless of the final ranking of the 2018 heatwave in the UK, it occurred with a different climate background. The heatwave, alongside record-breaking heatwaves across the Northern Hemisphere, is symptomatic of climate change. It has a different meaning in today’s world.

I did not in any way expect the response the tweet gained – with close to 14,000 likes a week later. Initially, I thought it might rile up a few ‘climate change deniers’ (I had a genuine interest in what might get said in response…) but after it surpassed by previous highest like/retweet count within a few hours, I knew something special was happening! I have no real idea of how far and wide the comparison went, as some didn’t relay any credit back to me for the original idea (e.g. a BBC News special “Feeling the Heat” which aired on July 26, and Met Office blog post using their HadCRUT data). Not that it bothers me – they are NASA’s graphics, after all, and I’m just happy to get a conversation going. Special thanks to Leo Hickman of Carbon Brief for helping me keep track of the various media appearances!

I’ve been looking at NASA’s GISS maps for years – the plotting tool on their website is a fantastic way to play around with climate data. Seeing a comparison like 1976 vs 2018 wasn’t surprising to me, but it occurred to me that the public don’t regularly see imagery like that – especially in such a relevant and meaningful way. It told a story. Telling the general public that the globe is X degrees warmer than it was 100 years ago, or showing them a line graph doesn’t really work – hence the success of my tweet and other novel visualisation ideas, such as the ‘climate spiral’ and ‘warming stripes’ by Professor Ed Hawkins – the original climate science viral sensation from the University of Reading! As I stated in the tweet thread, graphics like those I posted shouldn’t be surprising – global warming isn’t new, and the planet has been much warmer (relative to normal) than it is currently (try plotting February 2016 for a real shock).

Perhaps initiated by my tweet, or perhaps a coincidentally, the media – and scientists – quickly began widely discussing the relationship between climate change and the heatwaves across the Northern Hemisphere. The tweet seems to be the reason why the phrase ‘global heatwave’ gained so much use – I have seen it used before my tweet, but my use of that as a hashtag seems to have made it mainstream. It is not meant to suggest everywhere is under heatwave conditions – just that this heatwave is part of something bigger; that the planet itself is warmer than normal (i.e., a ‘heatwave’). It’s perhaps a bit of flippant phrasing which I can understand disagreement with.

However, whilst this has been the best-reported and most clear-cut example of linking climate change to ongoing weather, it did strike me that in some cases it was reported as though this was, in some way, new. A BBC News article from August 2003 (“Heatwave part of global trend”) could have been extracted word-for-word and used in 2018. The story then: a heatwave in the UK, but also deadly heatwaves around the world as global temperatures rose. 15 years later, and the story is the same. Yes, we have come a long way in 15 years in terms of our understanding of the climate, but the story is the same and the expectations are (broadly) the same. How long until it is accepted that the future we predicted is now happening? How long until we stop speaking of ‘heatwaves are expected to become more common due to climate change’? Climate change isn’t something we should continuously speak of in the future tense – it has happened and it is happening.

If you’ve read this far and are still with me, I added some of my ‘in the moment’ thoughts on July 24 to my first post on Reading’s Meteorology PhD blog site, “The Social Metwork”.

Right. What do I tweet next?

Record-Warm Global Temperatures

Over the past 18 months, global temperatures have been regularly breaking records, on both the surface-based (NASA, NOAA, Met Office) and the remote sensing records (UAH, RSS). Yes, this has been occurring now due to the 2nd strongest (by 3-monthly Nino 3.4 anomalies) El Nino on record. But I would argue, in many news broadcasts or articles, that the role of El Nino is regularly overstated – as though the reason for record-setting global temperatures is entirely ‘natural’ and should not be cause for alarm. This is not the case. Merely having an El Nino doesn’t guarantee a new record, without the background GHG forcing. It would be harder to argue that point if the current El Nino was by far and away the strongest, but it isn’t – 1982/3 (+2.1) and 1997/8 (+2.3) were similar to 2015/16 (+2.3).

The El Nino-Southern Oscillation (ENSO) is a big, noisy oscillator on global temperatures. There are other, slower factors (like the PDO and AMO), but ENSO is the biggest contributor year-on-year. Warming due to increased GHG forcing continues in the background, whilst ENSO causes these short-term fluctuations and will ‘make-or-break’ a year when it comes to setting records. It’s therefore natural that El Nino years set the records, as they spike temperatures upwards – it wouldn’t be the case that a La Nina year would result in a record. Notable is 2005, which was, at the time, a record-warm year, but ENSO neutral (a weak El Nino occurred in boreal winter 2004/5). Fig.1 shows this most clearly.


Figure 1: NOAA monthly global temperature anomalies coloured by ENSO conditions.

2015 was the warmest calendar year on record according to NASA’s GISTEMP record and NOAA’s NCDC record. However, it was not very strongly affected by El Nino – perhaps only around 10% of the warmth was due to ENSO – as the event was only developing during the year. With a lag effect of the warming Pacific on raising atmospheric temperatures, without increased GHGs it would not have beaten the 1998 value as much as it did (a 1951-1980 GISS anomaly of 0.87°C in 2015, compared with 0.63°C in 1998). It’s a tad ‘brute force’ (and not perfect) to do, but taking all other things to be equal, the difference of 0.24°C between those values is a trend of 0.14°C/decade.

This trend is of note due to the overhyped ‘global warming pause’ that seemed evident in the early part of the 21st century. Often exaggerated by skeptics who picked 1998 as a year to start a linear trend, it is something which seems to be evident in all datasets to differring extents – whether or not it is worth considering is still argued by different scientists. Many potential reasons exist – a change to a cool PDO and persistent La Nina conditions in 2007-2014 is something I always return to as a reason, particularly because since the PDO turned positive in 2014, temperatures have spiked, significantly. Fig. 1 strikingly shows the magnitude of recent warming, suggesting any pause/hiatus/slowdown is over – we will see the picture clearly in the next La Nina year.


Figure 2: NASA GISTEMP monthly data from Jan 1997 to June 2016. Credit

2016 is now looking very likely to beat 2015 (the first 6 months were the warmest half-year on record), which would make the top 3 record-warm years on the surface datasets 2014, 2015 and 2016 – rather remarkable. 7 consecutive months from October 2015 – April 2016 saw GISTEMP anomalies above 1°C relative to 1951-1980, which had never been observed before. The magnitude of the final 2016 anomaly depends on the strength of the developing La Nina, which is currently expected by most models to be rather weak. Fig. 3 shows a plume of various model forecasts. It’s worth noting 2010 set a new record at the time despite a strong La Nina developing in the 2nd half of the year.


Figure 3: ENSO model plume. Credit IRI.

Now for a brief comparison of the GISS and UAH records. NASA’s record is often accused of being the warmest (using a 1200km smoother to cover regions of sparse data, something which doesn’t actually alter the end result as much as some argue) whilst the UAH is a skeptic-friendly dataset, mainly because the 1998 El Nino spike was rather more severe. Fig. 4 shows a comparison of their records for June (the warmest in the GISTEMP record, and the 2nd warmest in the UAH record behind 1998).


Figure 4: Comparison of UAH and GISTEMP records for June 1979-2016 w.r.t. 1981-2010.

There are slight differences, and indeed the trends are slightly different. But the broad picture is the same. They differ on exact monthly rankings, as one would expect, but it’s not as though the UAH record shows global cooling, is it? (I’d argue satellite temperatures exaggerrate the ENSO influence – note how the 1998 El Nino spike and the 2008 La Nina dip are bigger).

A final note is inspired by a Twitter discussion I had and considers climatic averages. NOAA use the entire 20th century, NASA use 1951-1980 whilst UAH use 1981-2010. In the case of the latter, it’s enforced due to the data beginning in 1979. But is 1951-1980 or the full 20th century appropriate?

Local climate statistics are updated to reflect the new averaging periods and the ‘changing climate’, which is meaningful for the public (I don’t particularly care about knowing whether England was warmer than the 1961-1990 average, as I didn’t ever experience that, whereas 1981-2010 has meaning to me). However, when it comes to the globe as a whole, updating averaging periods would only confuse the message – suddenly these massive anomalies would become smaller, whilst you can’t actually ‘feel’ the anomaly, unlike for local regions. Moreover, as the 1981-2010 period exhibited such strong warming (whereas 1951-1980 was almost neutral) the average never truly existed. To best communicate the data, the anomalies should reflect the amount of warming that has taken place. For that reason, the full 20th century average (which is very similar to 1951-1980) would be my preference when it comes to the surface based temperature datasets.