Great Scott! 'Doc' Brown harnesses lightning using historical climatology!

Just over a couple of weeks ago, on October 21st, it was the 30th anniversary of the release of legendary sci-fi 80's classic ‘Back to the Future’.

If you like the film, you'll no doubt remember Emmett 'Doc' Brown - the mad scientist who builds a time machine (housed in a DeLorian sports car). Our hero, Marty McFly, gets stuck in the past and has to work out how to get ‘Back to the Future’. Upon reminiscing on this film, it occurred to me that when 'Doc' refers to himself as “a student of all sciences” he is including historical climatology. 

***SPOILER ALERT***

In the film, they need to find an energy source big enough to power the time-travelling DeLorian back in the 1950's. ‘Doc’ notices a “Save the Clock tower” flyer from the future, showing exactly when a lightning strike will hit the town's clock tower, which coincidentally, is set to happen in just a few days time. Madcap shenanigans ensue, but they end up performing the ultimate in verification of their historical climatological evidence when they manage to take advantage of this information to harness the power of the lightning strike, to send Marty back to the future!

Marty's flyer in "Back to the Future". Source: http://backtothefuture.wikia.com/wiki/Clock_Tower_flyer

This is actually a pretty good (fictional) example of how evidence derived from human society might relate to past weather records, especially for extreme or newsworthy events. Much of the uncertainty in the detail of how our climate has changed is down to a lack of data, and so using new sources of information is an important element of any discussion on climate change. 

With that thought in mind, for this blog, I have investigated historical climatology to study climate through human history (the Anthropocene), and how it may be used to support palaeoclimatological data which differs in that it studies climate throughout the history of the Earth.

It’s how you tell ‘em

In general, from checking a number of definitions, anecdotal evidence differs to scientific evidence in that it cannot be proven or disproven using scientific means. Historical climatology generally only stretches back a few thousand years too, since it focuses on the study of climate through representations in human historical evidence. The goal of a historical climatologist is to use what evidence can be gleaned from anecdotal and more official human records to infer observations about the climate. A good background of the different sources of historical climatological data was put together by Phil Jones in 2008. Data sources include:

• old news paper reports and photographs,
• mariner’s reports,
• town hall records,
• agricultural records,
• old maps,
• and one I am particularly intrigued by and probably more appealing than most other sources of ‘data’, the use of old paintings, and even cave paintings.

Here are some great old pictures (collated by ITV from PA) of the cold winter of 1963 in the UK, with parts of the River Thames apparently frozen. And further back still, here’s an old painting from 1683 of a Frost Fair,

Thames Frost Fair, 1683-84, by Thomas Wyke. Source: Wikipedia.com

and another from 1677 of the Thames freezing over with London Bridge in the background by Abraham Hondius.

The Frozen Thames, 1677, by Abraham Hondius. Source: Wikipedia.com

There are many depictions of cold weather through the 17th Century that coincide with the “Little Ice Age” and therefore it might seem to be a causal link. However, a lot has changed since the 17th Century. The river Thames for example was wider and shallower in places, and human structures such as the various bridges and flood defences, would have also affected river flow differently, perhaps allowing for freezes to occur in the past.

In short, many other factors determine whether a river freezes over, aside from temperature alone. I was asked about whether the Thames could freeze again while working as a weather forecaster, just a few years ago with the cold winter in 2010, and the question normally crops up during any cold winter season, as it certainly captures the imagination whenever freezing weather arrives in London. There is more on this subject at RealClimate.org here. This article goes on to describe how one of the most useful applications of anecdotal evidence is in the assessment of glacial retreat and ice melt.

Cool photographic evidence

A recent paper in Nature by Anders A. Bjørk et al. in 2012 uses 80-year old photographs of southeast Greenland to gain an insight into glacier and ice cover before satellite data became available. Photography offers greater ability to measure and analyse than an artistic impression, and so in this way, this paper was able to characterise some glacial responses over recent decades and link them to external forcings. It discusses how the warming in air and sea surface temperature led to rapid glacial retreats, but the study also notes that those glaciers that stop over the sea may respond faster than those terminating on land. A good article here covers the paper also.

Proxy validity?

It is important to validate any proxy information so, where data is sparse, alternatives should be considered. Historical climatology plays a part here, and can provide useful evidence if properly analysed. The main use would be to validate scientifically derived climate information from sources that can extend further back in through antiquity and beyond. By providing analogues (periods or events when both datasets agree), historical climatology might help to give validity and confidence to other datasets such as palaeoclimatoloical proxies. The main sources of palaeoclimatological records include:

• ice cores (essentially compacted snow over millennia is examined and useful information can be extruded using thickness of layers and the analysis of trapped air to find and measure oxygen isotopes, pollen or volcanic ash)
• tree rings (dendroclimatology can provide information on growth rates of different tree species which allows us to deduce information about the climate),
• corals (sclerochronology is essentially like using tree rings, but different variables of the atmosphere and oceans are represented),
• sediment layers in lakes.

Related to my main topic of storms, lake sediments can be used in to measure storm activity in the past. The method is quite opportunist and cannot be applied everywhere (perhaps a bit like anecdotal evidence in that respect) but basically involves using lakes that routinely hit by storms, or storm surge, and measuring indicators of erosion from flooding and/or incursions of sea water that build up, into the sediment layers, over the years.

There are numerous studies that infer storm and flood rates and intensities from lake sediments such as Gilli et al. in 2013, Vermaireet al. in 2012, and Page et al. in 1994. Through using lake sediments to look at salt water incursions, one recent paper by Donnelly et al. published in February this year, suggests that pre-historic storms (before the mid-1800s) on the NE coast of the US were more intense than anything we have seen in the historical records. It seems that this is a chief proxy for looking into palaeotempestology. This has peaked my interest, so I’ll be looking at lake sediments and storm surge again in more detail in future blogs.

Everyone loves a good story

I have learnt that evidence analysed by climate historians is difficult to link with the more scientifically collected evidence from palaeoclimatological proxies, but it can provide a degree of verification if used carefully as discussed above. Some cases, such as using old painting and photographs, certainly capture the imagination easily, and old mariner’s reports and documentary accounts can be equally compelling. Perhaps its power is also effectively focussed on public engagement, allowing a narrative and immediacy that many graphs and figures do not. I’m sure the idea of science communication and engagement will come up again in my blog as I do find it fascinating.

New sources of weather data

So aside from Doc Brown using historical evidence in the form of an old flyer, Anders A Bjørk using old photos to study glaciers, and palaeoclimatologists using a whole host of proxies for peering further back in time through the ages, I’ve also wondered what types of past evidence there will be in the future, aside from our ongoing weather observations network. In a world of Big Data, there is plenty of unverified but still potentially valuable data around. With the dawn of the internet, we have become able to share and consume data from virtually anywhere on the planet.

Social media and smart phone technology provides unprecedented accessibility to environmental data. “Citizen Science” crowdsourcing projects such as mPING from the National Severe Storms Laboratory, or the Met Office's Weather Observations Website (WOW) provide portals for the general public to upload weather reports that can be used to improve forecasting.

mPING report data. Source: NSSL mPING website.

These are not calibrated observations by professional staff or sensitive equipment, but they do potentially provide a coverage and density of data points that cannot be matched by conventional ground-based weather observing. Calibration can be performed, by using other sources of data such as radar, satellite imagery and more credible weather stations. It is the hoped that this kind of data can provide better information on extreme weather events in the future.

Back to the beginning

But thinking back to the storm that started this line of enquiry - the fictional thunderstorm that hit the small fictional town of Hill Valley - it’s easy to find ourselves a little envious of ‘Doc’ and Marty. I find myself musing that if we had the time-travelling DeLorian, we could go back to verify as much historical or palaeoclimatological data as we want. Better yet, we could even warn our past selves that climate change would become such a major global issue, and advise ourselves that we should at least start thinking seriously about a more sustainable future.

Although, as we know from most films involving time travel, things always go wrong when you start messing around with the past. Perhaps, it’s best that we must stick to learning what we can from what’s left behind for us to find.