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Like many people, the first graph I ever saw explaining climate change was in a school geography textbook. It showed the听鈥渉ockey stick鈥� curve听of the Earth鈥檚 surface temperature over time, which has become one of the world鈥檚 most recognisable line graphs.

Despite relatively minor fluctuations, the line on the graph depicting global surface temperature remains almost horizontal across centuries, before suddenly inclining to an almost vertical trajectory over the past 50 years. Since 1970 the rate of global temperature increase has hit an unprecedented听1.7掳C per century.

One challenge of understanding the information contained in this hockey stick graph 鈥� and this is a gift to climate-change deniers 鈥� is the inclusion of the grey fuzz of 鈥渦ncertainty data鈥�: outlying data points that can be cherry-picked to raise doubts about the mass of evidence supporting a general warming trend.

Uncertainty is a complex thing to communicate in a single chart. In 2018 the UK-based climate scientist Ed Hawkins chose to omit it altogether when he presented his 鈥�warming stripes鈥� graphic to help clearly visualise key trends in climate data. Hawkins explained that the warming stripes were designed to remove all superfluous information, leaving behind only the undeniable scientific evidence of a steadily warming world.

If getting to grips with all the data and complexity in the hockey stick required a long read, Hawkins鈥� climate stripes give us the headline. The stripes are now a听global phenomenon, having appeared on the lapels of US senators, the ties of TV weather presenters and on the front cover of The Economist.

As calls for change grow louder in light of the latest听IPCC (Intergovernmental Panel on Climate Change) report听and in the run up to听COP26听conference in Glasgow this November, it鈥檚 time to focus on how data visualisation can help people grasp the challenges that lie ahead.

One misconception about the climate crisis is that warming will be uniform across the world. Deniers cite cold fronts or blizzards as evidence that warming is exaggerated, or hark back to past heatwaves 鈥� such as that experienced by the UK听in 1976听when temperatures exceeded 35掳C 鈥� as proof that the scientists have got it wrong.

Apart from this听misleading conflation听of weather (daily conditions) and climate (long-term conditions), this kind of argument misses the complex patchwork of effects that interact to create what gets reported in the headline figures.

Maps can be an invaluable weapon against this misunderstanding. For the first time, the IPCC has released an 鈥渋nteractive atlas鈥� with its latest report, allowing audiences to pan and zoom through the data themselves. But if you give the听IPCC鈥檚 atlas听a try, you can see how it鈥檚 hard to capture complexity for a specialist audience while retaining simplicity for a global audience.

Most users are unlikely to closely engage with towering datasets named 鈥楥MIP5鈥� or 鈥楢PHRODITE鈥�, or with the mass of code that constitutes the IPCC-WG1 repository on听Github. Although it鈥檚 a step in the right direction, what is needed are more universally听accessible visualisations听that are able to show where we鈥檙e heading in no uncertain terms.

With that in mind, when I set out to map global warming for a new book entitled听Atlas of the Invisible, my co-author听Oliver Uberti听and I chose to combine the most important lessons from the warming stripes with the intricacies of geographical context.

This intriguingly named 鈥淧eirce quincuncial鈥� projection, which you can see below, is a type of 2D map that flattens the Earth into a grid of 130 mini maps called tiles. Like all projections, it鈥檚 not a perfect representation of the 3D Earth, since some areas are stretched more than others. But it lets us create a series of tiles representing the planet in each year from 1890 to 2019, coloured by how and where temperatures deviated from a听reliable baseline听measured between听1961 and 1990. Blue areas represent temperature anomalies between -2掳C and 0掳C, while red areas represent anomalies between 0掳C and 3掳C and grey represents insufficient data.

Reading the images from left to right reveals that while heatwaves and cold spells speckle the grid, tiles representing the current century are increasingly filled with warm tones. For example, compare the few pink splotches in 1976 when the UK experienced its famous heatwave to years later in 2006 and 2016 when ruddy hues spanned the globe. In fact, the听ten hottest years听on record have occurred since 2005.

When mitigation targets aim to keep the overall global temperature increase at an average of below 1.5 or 2掳C, we need data visualisations to remind us that there can still be large local variations even when such targets are achieved, with the warming creating drastic and often devastating conditions for those living in affected areas.

Generalised warming will inevitably affect some places far worse than others, causing听knock-on effects听like sea-level rises and storms in different areas. For proof, look to the 2021听summer heatwave听experienced by many parts of Europe yet escaped by the UK, the 鈥渉eat dome鈥� that scorched British Columbia in June, or the Arctic, where temperatures are rising at twice the global rate.

Even within cities, conditions can vary from neighbourhood to neighbourhood. Across the US, global warming is compounding the legacy of racist housing policies enacted through a process known as听redlining. This rated the 鈥渋nvestment risk鈥� of听urban areas, condemning many black neighbourhoods to a听鈥渉azardous鈥� rating听and thus to reduced infrastructure and increased poverty.

As听the New York Times听has expertly mapped, such areas saw a lack of investment in 鈥� amongst other things 鈥� green spaces and street trees. This has resulted in some historically听redlined neighbourhoods听suffering summers that are up to 7掳C warmer compared to their non-redlined counterparts.

Maps reveal these social injustices in the UK, too.听Local authorities听are under pressure to turn a blind eye to flood-risk maps in order to permit thousands of听鈥渁ffordable鈥� homes听to be built for those priced out of higher ground.

The power of maps lies in their ability to show us simultaneously that as global average temperatures rise, local conditions threaten to become ever more extreme. We now need to better harness that power to inspire action.

This article first appeared in on 12 August 2021.

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• 白小姐论坛 Faculty of Social and Historical Sciences