2020, Roelfsema, Mark, van Soest, Heleen L., Harmsen, Mathijs, van Vuuren, Detlef P., Bertram, Christoph, den Elzen, Michel, Höhne, Niklas, Iacobuta, Gabriela, Krey, Volker, Kriegler, Elmar, Luderer, Gunnar, Riahi, Keywan, Ueckerdt, Falko, Després, Jacques, Drouet, Laurent, Emmerling, Johannes, Frank, Stefan, Fricko, Oliver, Gidden, Matthew, Humpenöder, Florian, Huppmann, Daniel, Fujimori, Shinichiro, Fragkiadakis, Kostas, Gi, Keii, Keramidas, Kimon, Köberle, Alexandre C., Aleluia Reis, Lara, Rochedo, Pedro, Schaeffer, Roberto, Oshiro, Ken, Vrontisi, Zoi, Chen, Wenying, Iyer, Gokul C., Edmonds, Jae, Kannavou, Maria, Jiang, Kejun, Mathur, Ritu, Safonov, George, Vishwanathan, Saritha Sudharmma

Many countries have implemented national climate policies to accomplish pledged Nationally Determined Contributions and to contribute to the temperature objectives of the Paris Agreement on climate change. In 2023, the global stocktake will assess the combined effort of countries. Here, based on a public policy database and a multi-model scenario analysis, we show that implementation of current policies leaves a median emission gap of 22.4 to 28.2 GtCO2eq by 2030 with the optimal pathways to implement the well below 2 °C and 1.5 °C Paris goals. If Nationally Determined Contributions would be fully implemented, this gap would be reduced by a third. Interestingly, the countries evaluated were found to not achieve their pledged contributions with implemented policies (implementation gap), or to have an ambition gap with optimal pathways towards well below 2 °C. This shows that all countries would need to accelerate the implementation of policies for renewable technologies, while efficiency improvements are especially important in emerging countries and fossil-fuel-dependent countries.

2016, Kreidenweis, Ulrich, Humpenöder, Florian, Stevanović, Miodrag, Bodirsky, Benjamin Leo, Kriegler, Elmar, Lotze-Campen, Hermann, Popp, Alexander

Ambitious climate targets, such as the 2 °C target, are likely to require the removal of carbon dioxide from the atmosphere. Afforestation is one such mitigation option but could, through the competition for land, also lead to food prices hikes. In addition, afforestation often decreases land-surface albedo and the amount of short-wave radiation reflected back to space, which results in a warming effect. In particular in the boreal zone, such biophysical warming effects following from afforestation are estimated to offset the cooling effect from carbon sequestration. We assessed the food price response of afforestation, and considered the albedo effect with scenarios in which afforestation was restricted to certain latitudinal zones. In our study, afforestation was incentivized by a globally uniform reward for carbon uptake in the terrestrial biosphere. This resulted in large-scale afforestation (2580 Mha globally) and substantial carbon sequestration (860 GtCO2) up to the end of the century. However, it was also associated with an increase in food prices of about 80% by 2050 and a more than fourfold increase by 2100. When afforestation was restricted to the tropics the food price response was substantially reduced, while still almost 60% cumulative carbon sequestration was achieved. In the medium term, the increase in prices was then lower than the increase in income underlying our scenario projections. Moreover, our results indicate that more liberalised trade in agricultural commodities could buffer the food price increases following from afforestation in tropical regions..