Why scientists have modelled the climate up to the year 2300

Yorkshire, in the year 2218, probably. (Actually Mexico.) Image: Getty.

The seas will continue to rise for 300 years. That’s the conclusion of a new study, published in Nature Communications, which projects how much the sea level will rise under varying degrees of success in tackling climate change right up to the year 2300.

But 2300 is almost three centuries from now. Three centuries ago the industrial revolution hadn’t even started. This raises the question of whether, when considering present-day climate policy, there is any value at all in considering such distant futures.

After all, the Paris Agreement on climate change hasn’t set its global temperature rise targets beyond the end of the current century. And even this appears too remote a horizon to motivate emissions cuts in the near future. Therefore, Paris focuses on five-year climate policy cycles starting in 2018, which are more in line with typical political and business cycles, and in tune with our everyday concerns.

Nonetheless, multiple climate studies do consider projections of the far future. For instance, one paper estimated that, if we fail to tackle climate change, the Arctic Ocean could be ice-free all year round somewhere between 2150 and 2250. Another study looked at carbon emissions from thawing permafrost as far out as the year 2500.

The obvious criticism is that such work is mere fiction, driven by the intellectual curiosity of a small group of highly specialised scientists, rather than anything relevant to daily life. And in any case, critics might argue, won’t we figure something out in the next century or two that could tackle climate change and prove all the predictions of doom and gloom unfounded?

Emissions will still be linked to the economy

As is often the case, the truth is a little bit more complex.

The first thing to note is that a certain amount of climate change is already “locked in”. Our use of energy and other resources is not going to slow down any time soon, as poorer countries race to industrialise and catch up with the global leaders, while more affluent nations aim to maintain and further improve their living standards. Most people can relate to these aspirations, even if the upshot is they ensure that global emissions stay at their current high levels.

Solar and wind power will of course help, but the reality is that such technologies are still nowhere near enough to radically alter the link between emissions and economic expansion. Despite the renewables boom, 2017 saw a 2 per cent rise in global emissions following a three-year plateau. Experts argue that making serious emissions cuts will require much more ambitious efforts across nearly all economic activities, including energy, urbanisation, infrastructure, transport, heavy industries and land use.

We can predict future growth

This brings us back to the very long-term scenarios used by climate scientists. These scenarios are actually based on credible assumptions about a large set of long-term socio-economic and technological drivers that define contrasting futures for the world as a whole. And it turns out that things which will affect future emissions and climate, like the rates of technological progress, or population and wealth growth, are likely going to be constrained within a reasonably predictable range. Even if one includes the possibility of “game-changing technologies”, for example a hypothetical new generation of much cheaper and more effective batteries for electric cars, the world is almost certainly going to stay within this range of scenarios.

This is where climate science comes into play. As certain physical processes triggered by global warming are relatively slow, their full impact won’t be apparent for hundreds of years. Consider the ice sheets found in Greenland and Antarctica, for instance, both so big that they respond to climate change only slowly. However, once triggered, and the ice starts sliding towards the oceans, causing the sea level to rise, the melting process takes centuries to reverse. Something similar is happening with thawing permafrost, which releases additional greenhouse gases into the atmosphere.

Both rising sea levels and thawing permafrost could impact hundreds of millions of people, particularly those living in coastal areas or hotter climates. But if we want to know how much we should be worried, then climate predictions up until 2050 won’t cut it – the world may still be warming at that point, even if we stopped emitting carbon overnight. Given the future of the world is bound within a reasonably predictable range of scenarios, it therefore makes sense to estimate the risks posed by these slow physical processes, by extending the analysis as far out as 2300.

Why sea levels in 2300 matter

I believe it’s a ‘climate agreement’, captain. They were popular in the 21st century. Image: NBC.

Back to the original study. Its main result was that the sea level could still rise by up to 1.2 metres (4ft) by 2300 even under a very optimistic climate scenario where the global temperature never rises more than 2℃ above pre-industrial levels. That is, even if manmade emissions peak within the next two decades, then drop down to zero no later than by 2070 and remain at zero from then onwards – sea levels would still rise by more than a metre.

Achieving zero net emissions within the next 30 to 50 years will be hard enough. But the study shows that even if this ambitious target is achieved, sea levels will continue to rise for the following two centuries. This is a climate time bomb for coastal areas. Though it may not seem like a lot, a 1.2-metre sea level rise will still force megacities such as London and New York to spend billions to maintain flood defences in the face of stronger storm surges.

Achieving zero emissions is therefore not enough to prevent the long-term effects of sea level rise from kicking in. To bring temperatures back to at least the current levels – that is around 1℃ above pre-industrial – we’ll need negative emissions technologies that draw carbon directly out of the atmosphere.

The ConversationThis is an important long-term policy result that was made possible by considering extended time horizons. By reaching as far out as 2300, we have reaffirmed the need to take ambitious climate action in the more immediate future.

Dmitry Yumashev, Senior Research Associate, Pentland Centre for Sustainability in Business, Lancaster University.

This article was originally published on The Conversation. Read the original article.


To beat rising temperatures, Vienna launches a network of 'Cool Streets'

A Vienna resident cools off at one of the city's new Cool Streets installations. (Courtesy Christian Fürthner/Mobilitätsagentur Wien)

Over the past several months, Austria has recorded its highest unemployment rate since World War II, thanks to the economic aftermath of the Covid-19 pandemic. With no job or a suddenly smaller income – not to mention the continued threat of the virus – many Viennese will opt for a staycation this summer.  

At the same time, last year, Austria’s capital experienced 39 days with temperatures of over 30°C (86°F), one of its hottest summers in history according to the Central Institute for Meteorology and Geodynamics.

Climate experts expect a similarly sizzling 2020 season, and city officials are now doubling down on efforts to combat the heat by launching a “Cool Streets” initiative as well as a new, state-of-the-art cooling park.

“As the city councilwoman in charge of climate, it is my job to ensure local cooling,” Vienna’s deputy mayor Birgit Hebein proclaimed at the opening of one of 22 new “Cool Streets” on 22 June.

“In Austria, there are already more heat deaths than traffic fatalities,” she added.

Hebein was referring to the 766 people the Austrian Agency for Health and Food Security included in its 2018 heat-associated mortality statistics. The number was up by 31% compared to 2017, and in contrast to the 409 people who died in traffic collisions the same year.

The project includes 18 temporary Cool Streets located across the city, plus four roads that will be redesigned permanently and designated as “Cool Streets Plus”.

“The Plus version includes the planting of trees. Brighter surfaces, which reflect less heat, replace asphalt in addition to the installation of shadow or water elements,” said Kathrin Ivancsits, spokeswoman for the city-owned bureau Mobilitätsagentur, which is coordinating the project.

Vienna's seasonal Cool Streets provide shady places to rest and are closed to cars. (Petra Loho for CityMetric)

In addition to mobile shade dispensers and seating possibilities amid more greenery provided by potted plants, each street features a steel column offering drinking water and spray cooling. The temporary Cool Streets will also remain car-free until 20 September.

A sensor in the granite base releases drinking water and pushes it through 34 nozzles whenever the outside temperature reaches 25°C (77°F) . As soon as the ambient temperature drops to 23°C (73°F), the sensor, which operates from 10 a.m. to 8 p.m., turns off the water supply.

The sensors were included in part to allay concerns about legionella, a pathogenic bacteria that can reproduce in water.  

“When the spray stops, the system drains, and therefore no microbial contamination can develop,” said Dr. Hans-Peter Hutter, deputy head of the Department of Environmental Health at the Center for Public Health at Medical University Vienna, in a televised interview.

Hutter also assured the public that there is no increased risk of a Covid-19 infection from the spray as long as people adhere to the one-meter social distance requirement.

But Samer Bagaeen of the University of Kent's School of Architecture and Planning notes that air cooling systems, like the ones used in Germany at abattoirs, have been found recently to be a risk factor for Covid-19 outbreaks.

“The same could be said for spay devices,” he warned.

Vienna’s district councils selected the 22 Cool Street locations with the help of the city’s Urban Heat Vulnerability Index. The map shows where most people suffer from heat by evaluating temperature data, green and water-related infrastructure, and demographic data.

“Urban heat islands can occur when cities replace the natural land cover with dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat,” as the US Environmental Protection Agency states.

A rendering of Vienna's planned park featuring a Coolspot, which is scheduled to open in August. Click to expand.
(Courtesy Carla Lo Landscape Architecture)

Vienna’s sixth district, Mariahilf, is such an area. The construction of the capital’s first “Cooling Park”, a €1 million project covering the 10,600 square-metre Esterházypark, is designed to provide relief. 

Green4Cities, a centre of excellence for green infrastructure in urban areas, designed the park’s main attraction, the “Coolspot”. The nearly 3.40-metre high steel trellis holds three rings equipped with spray nozzles. Textile shading slats, tensioned with steel cables, cover them.

The effects of evaporation and evapotranspiration create a cooler microclimate around the 30 square-metre seating area, alongside other spray spots selectively scattered across the park.

The high-pressure spray also deposits tiny droplets on plant and tree leaves, which stimulates them to sweat even more. All together, these collective measures help to cool their surroundings by up to six degrees.

The landscape architect Carla Lo and her team planned what she calls the “low-tech” park components. “Plants are an essential design element of the Cooling Park,” Lo says. “By unsealing the [soil], we can add new grass, herbaceous beds, and more climate-resistant trees to the existing cultivation”.

Light-coloured, natural stone punctuated by grass seams replaces the old concrete surfaces, and wooden benches meander throughout the park.

Living near the park and yearning for an urban escape close by, Lo says she’s motivated to ensure the park is completed by mid-August.

“If we don't do anything, Vienna will be another eight degrees Celsius hotter in 2050 than it already is,” Hebein said.

Vienna recently came in first in the World's 10 Greenest Cities Index by the consulting agency Resonance.

“There is no one size fits all on how cities respond to urban heat,” says the University of Kent’s Bagaeen, who points out that Vienna was one of the first European cities to set up an Urban Heat Islands Strategic Plan in 2015.

In the short term, prognoses on the city’s future development may be more difficult: Vienna votes this autumn.

Petra Loho is a journalist and photographer based in Austria.