Demystifying climate change

To kick off our new Climate Column, Tom Hollands explains some of the major characteristics of climate change and takes on some of the arguments commonly put forward by so-called ‘climate sceptics’.

Written by: Tom Hollands

Art by: Winnie Lei

Barely a week goes by without headlines of melting ice sheets, rising sea levels and increasing global temperatures. Whatever one’s opinion, climate change is undoubtedly a hot topic. Most newspaper articles defer to the authority of expert scientists, but few column inches go toward explaining what climate change actually is. So-called ‘climate scepticism’ is still rife, and building climate policy discussions from a foundation in established atmospheric science is the best antidote to this. Climate change will dominate public discourse for generations to come – it is down to all of us us to better understand it.

Building Blocks

Before engaging in a discussion about climate change, it is worth distinguishing between climate and weather. Weather is local and temporary: the weather in London this morning (as always) was overcast, with a chance of rain. Climate can be local, but is an average over a period of time. Since climate is a statistical variable, when we talk about climate change, we are talking about a change in an average, which can mask substantial variations in day-to-day weather. Incidentally, it is worth pointing out that when most scientists talk about climate change, they mean global climate change; changes in local micro-climates are interesting but are seldom the focus of world news.

Climate change is a result of the interplay of various factors, some of which are natural, and some of which are anthropogenic (human-driven). The single largest influence is the concentration of greenhouse gases, which absorb outgoing electromagnetic waves and re-emit them so more energy remains within Earth’s atmosphere. Historically, the concentration of greenhouse gases has fluctuated in line with clear ecological and geological timelines. However, since the industrial revolution of the nineteenth century, greenhouse gas concentrations have skyrocketed.

Naturally, it’s Complicated

The atmosphere is a complex, interconnected system, and large natural events can influence the global climate. 1883 is sometimes referred to as ‘the year with no summer’. The earth’s interior belched, and the enormous volcano Krakatoa exploded. Spectacular sunsets were seen the world over, due to increased volcanic ash in the atmosphere. Global temperatures fell by more than 1°C, and it took years for them to return to normal. Aerosols, such as naturally produced volcanic ash and artificial particulates in consumer products, reflect incoming solar radiation which has a cooling effect on climate.

Atmospheric circulation naturally varies. When meteorologists talk about ‘El Nino’ or ‘La Nina’, they are referring to particular phases of the southern oscillation, in which sea temperatures and air pressures vary in regular, predictable ways. There are many other periodic oscillations which make up the global atmosphere, and all of them have an impact on global climate.

Hot and Cold?

In February 2015, amidst a tumultuous snowstorm, US Senator James Inhofe hurled a snowball across the senate floor. In his view, this was proof that climate change is a myth. A criticism often levelled by so-called climate ‘sceptics’ like Inhofe is that climate scientists use increasing temperatures and the accompanying hotter weather, as well as the increase in extreme weather events – including cold-weather storms – as evidence for climate change. How can both warm and cold weather be evidence for rising temperatures? It is only by considering climate statistically that this claim can be dismantled. A rise in yearly average global temperature is an aggregate of daily, regional, temperatures within which there will always be large seasonal and geographical variation. When climate scientists make claims about rising temperatures, they are almost always referring to such averages. The earth is trending globally towards warmer overall temperatures, despite plenty of local variation. It is this flagrant defiance of statistical averaging that Senator Inhofe demonstrated with his now-infamous snowball.

Crucially, extreme cold weather events can be evidence for climate change, but only if it can be demonstrated that the frequency of these events has altered. In the case of global warming, increasing movement of warm air from the tropics results in mid-latitude weather systems with more moisture and larger temperature gradients, especially in the winter months. The latter in particular provides more power for storms, so climate scientists expect the likelihood of extreme weather events such as Hurricane Katrina and Superstorm Sandy to increase.

Scepticism or Ignorance?

The motto of the Royal Society, the oldest existing society dedicated to scientific inquiry in the world is Nullius in verba – ‘take nobody’s word for it’. Climate change ‘sceptics’ position themselves as freethinkers, adhering to this motto while doubting the developments of atmospheric science, which they often see as an ‘establishment’ orthodoxy. Simultaneously, these ‘sceptics’ decry the ‘lack of consensus’ within the scientific community about climate change – having their cake and eating it. The reality is there is considerable doubt among climate scientists themselves, just not in the way the ‘sceptics’ imagine. Scientists are at home amongst uncertainty, and build their careers upon scepticism. The research establishing the link between greenhouse gas production and rising temperatures has withstood intense scrutiny, as has the rest of the evidence cited above. Scientists disagree on how this evidence should be interpreted, and how best to predict changes in climate. While there is substantial disagreement (and thus no ‘consensus’) on how much average sea levels will rise in 20 years, the overwhelming majority of climate scientists agree that sea levels will rise, and that this is a bad thing which should be mitigated.

There is no doubt that climate change is real, but it is not a doctrine, beyond discussion or criticism. On the contrary, a healthy dose of scepticism will help us understand climate change better. As time ceaselessly marches on, climate change will become a larger issue in our lives. Public discourse can only benefit from the intelligent discussion that informed scepticism brings.

Featured Image

‘Inspired by Jill Pelto and the ukiyo-e artist Hokusa, the illustration weaves a plot of global sea levels into the crest of the wave. The y-axis represents the quantities of sea height variation, and the x-axis depicts the timeline between April 2002 to January 2017.’ 

(GSFC. 2017. Global Mean Sea Level Trend from Integrated Multi-Mission Ocean Altimeters TOPEX/Poseidon, Jason-1, OSTM/Jason-2 Version 4. Ver. 4. PO.DAAC, CA, USA. Dataset accessed [2017-10-03] at 10.5067/GMSLM-TJ124.

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