A surprise in the international Paris Agreement on greenhouse gas emissions was the addition of the ambitious goal of limiting global warming to just 1.5 degrees Celsius. Nations have long stated that their goal was to prevent a warming of more than 2 degrees (although they have largely failed to take actions that would make that possible), and so scientists have pushed that scenario up to date. studied in detail. But nobody promised to keep this a 1.5-degree world, so the information was lacking.
A new study led by Joeri Rogelj of the International Institute for Applied Systems Analysis digs into this problem, providing an analysis of plausible scenarios that will form the basis for future research efforts. This work uses computer models of the global economy to simulate the costs and effects of such things as switching fossil fuels at different speeds.
Build scenario
The simulations are based on a series of five scenarios representing different socio-economic futures. This includes idealistic scenarios such as a world built around sustainability, with a world population of only 7 billion by the end of this century, rather than the expected 10 billion. At the other extreme, there is an all-consuming world in which energy demand is growing rapidly and is almost entirely met by fossil fuels. This system is a little easier to turn your head around than scenarios based purely on greenhouse gas concentrations, because you can imagine what these worlds really look like.
For each of these five worlds, the researchers are looking at whether their models can find a way to reduce greenhouse gas emissions enough to keep the world warming below 1.5 degrees by 2100 — even if it’s a few tenths of a degree higher. is for that. Come back down.
Given that our options to limit warming to 2 degrees Celsius already require a hey-maybe-the-glass-is-actually-full of optimism, it should come as no surprise that 1.5-degree scenarios will transform us massively. entail behaviour. Global emissions should peak within the next few years and then plummet – reaching zero around 2060. At our current rate of emissions, we would probably be emitting the maximum allowable total of greenhouse gases in less than ten years.
To prevent that, the use of coal for electricity generation should be phased out by 2050 and the use of oil should stop shortly after. Renewable electricity from sources such as solar and wind should make up 60-80 percent of our generation by the middle of the century. The role of natural gas varies widely between the different model simulations, ranging from more than a doubling to an 80 percent decrease.
These scenarios also require a crutch that is often invoked, even if it has yet to be widely used: running biofuel plants, capturing the emitted CO2and store it underground. Because the crops used as biofuels remove their carbon from the atmosphere, this costs atmospheric CO2 and pushes it into the ground while generating electricity along the way. This is not without its drawbacks, especially the need for agricultural land that would otherwise be used for food crops.
Capture carbon
This technique (and others that removed carbon dioxide from the air) must be widely used for the numbers to work in these scenarios. Reducing net emissions (released minus removed) to zero isn’t even good enough – we should remove Lake than we emit in the second half of this century. By 2100 we may need up to 30 years of CO. have deleted2 at the current emission. That would be a massive deployment of carbon dioxide removal techniques next a revolution in the energy sector.
If you compare this with the actions needed to achieve the target of a maximum of 2 degrees of warming, more removal of carbon dioxide is only part of that. The emissions reductions are stronger and faster, which means they are more expensive. And it’s not just energy sources that need to change – there also needs to be more efficiency and less demand for energy.
Overall, the researchers say there are some general socioeconomic trends in these scenarios. Scenarios that limit warming to 1.5 degrees see major shifts towards renewable sources of electricity, less energy consumption in general and a significant renewal of carbon dioxide. In contrast, the scenarios that fail to meet this target show energy-intensive economic growth, greater geographic inequality and a mish-mash of uncoordinated short-term climate policies.
The researchers say their work shows that “multiple technologically striking options are available,” but of course, this doesn’t mean any of them are likely to happen. The painted image is one of wafer-thin margins for error. Even capturing all CO2 originating from existing fossil fuel power plants would not be good enough, because the mere production of fossil fuels leaks too much greenhouse gas.
There is simply no escaping the fact that things would have to change immediately if we want that 1.5 or 2 degree future, regardless of the goals set during international negotiations. The world has hesitated for too long to still put an easy solution on the table.
Nature Climate Change2018. DOI: 10.1038/s41558-018-0091-3 (About DOIs).