In order to slow down climate change, a comprehensive switch to renewable energies is necessary. But even such an energy transition initially generates additional CO2 emissions, among other things through the production and installation of new wind turbines, solar systems and other systems. How many greenhouse gases will be produced by the global transition of energy systems depends crucially on the speed of the switch, as researchers have determined. With a rapid energy transition with the installation of almost six terawatts per year by 2050, the additional emissions by 2100 would be less than 20 billion tons of CO2. With a slower energy transition, the additional CO2 emissions would be up to nine times higher.
To avoid even worse consequences, global warming would need to be limited to 1.5 or 2 degrees above pre-industrial levels. This requires, among other things, an exit from fossil fuels and a conversion of the entire energy system to renewable sources such as wind, sun or geothermal energy. However, such a transition will not be possible without significant additional costs and also CO2 emissions. For the installation of wind turbines, solar panels and electricity storage, additional raw materials have to be mined and transported, and the production of concrete, steel and semiconductor components also costs energy. As long as there is not enough "green" electricity for this additional demand, at least part of this energy will have to be covered by fossil sources - and this generates additional greenhouse gas emissions.
How many emissions does the energy transition cause?
Corey Lesk from the Lamont-Doherty Earth Observatory at Columbia University in New York and his colleagues have now investigated how high the emissions for this transition are. In their study, they analyzed three areas in which climate protection and adjustments could lead to relevant additional CO2 emissions: the energy transition and the associated mass construction of systems for renewable electricity generation, the increasing cooling demand due to air conditioning and adaptation to sea level rise Coastal defenses and resettlement. For each of these three areas of action, they examined three scenarios: a rapid transition to achieve the 1.5 degree climate protection target, a more gradual change with the target of two degrees and a delayed transition corresponding to the current pace of the measures, which corresponds to a warming of 2. would amount to 7 degrees.
For the energy transition, the researchers assumed the installation of new systems with an output of 4.5 terawatts per year for the gradual scenario. Electricity production from the sun and wind would then reach a plateau around 2050 at around 100 terawatts and cover around 80 percent of global primary energy requirements. By 2080, renewable energy could then completely replace fossil fuels. In the scenario of rapid decarbonization, the annual installation rate is 30 percent higher at 5.9 terawatts of maximum output, with a delayed energy transition only around 2.6 terawatts of output per year will be newly installed by 2050.
The pace is crucial
The calculations showed that the three scenarios differ not only in the pace of decarbonization, but also in the extent of the additional CO2 emissions generated. Because the faster the available amount of renewable energy increases, the less fossil fuels are needed for the transition. "The message is that it takes energy to rebuild the global energy system and we need to take that into account," says Lesk. "But the way in which we approach this transition is not negligible: the faster you bring the renewables to the grid, the more the transition can also be supplied with these energies." As expected, the energy transition also generates more than 90 percent the lion's share of emissions compared to coastal defense and cooling.
In concrete terms, the researchers determined that if mankind manages the rapid changeover of energy systems, less than 20 billion tons of additional CO2 would be emitted. Because as early as 2030, almost the entire electricity requirement of the transition would be covered by wind, sun, hydropower, geothermal energy and co. In the gradual scenario, which the scientists also believe to be much more realistic, around 95 billion tons of additional CO2 emissions would be generated by the year 2100 alone for the energy transition. Together with coastal protection and cooling, it would be 96.3 gigatonnes of CO2. If, on the other hand, the energy transition were delayed and some of the energy was still generated from fossil fuels by 2100, the CO2 emissions for decarbonization would be 185 billion tons of CO2 – about twice as high. That CO2 output is equivalent to five to six years of total current global CO2 emissions, the team explains.
"Our values only indicate the lower limit," emphasizes Lesk. "The upward range could be much higher." On the one hand, only CO2 emissions were taken into account, not those of other greenhouse gases, which could account for another 40 percent. On the other hand, the raw material and energy requirements for secondary structures such as new power lines or power storage were not recorded. Indirect consequences of the increased extraction of raw materials such as deforestation and other changes in land use are also not recorded. "Despite these limitations, we conclude that transition emissions can be greatly reduced if decarbonization is accelerated," the researchers write. "This gives a new urgency to measures for the rapid switch to renewable energies." Because if the energy transition and decarbonization are delayed, the whole thing will not only become considerably expensive, it will also make climate protection more difficult.
Source: Corey Lesk (Lamont-Doherty Earth Observatory, Columbia University, New York) et al., Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.2123486119