Charting the Earth's Future
The 2021 Global Change Outlook continues a process, started in 2012 by the MIT Joint Program, of providing a periodic update on the direction the planet is heading in terms of economic growth and its implications for resource use and the environment. To obtain an integrated look at food, water, energy and climate, as well as the oceans, atmosphere and land that comprise the Earth system, we use the MIT Integrated Global System Modeling (IGSM) framework. Consisting primarily of the Economic Projection and Policy Analysis (EPPA) model and the MIT Earth System Model (MESM), the IGSM is a linked set of computer models developed by the MIT Joint Program to analyze interactions among human and Earth systems. As in our previous (2018) edition, this year’s Outlook reports on projected effects of population and economic growth, technology improvements, climate policy and other factors on energy and land use, emissions and climate, and water and agriculture. An important first step toward achieving stabilization of global average temperatures at reasonable cost is the Paris Agreement, in which nearly 200 countries committed to a wide range of initial climate actions aimed at achieving that goal. For this year’s Outlook, we have invited guest contributors to offer perspectives on the impact of the Covid-19 pandemic on economic growth, climate mitigation and public health, as well as the need for a systems approach to climate change and human health and well-being. Recognizing the inadequacy of the short-term commitments to keep global warming below the long-term targets of 2°C or even 1.5°C, we explore emissions pathways consistent with these goals.
About the 2021 Outlook
The 2021 Global Change Outlook presents the MIT Joint Program’s latest projections for the future of the Earth’s energy, managed resources (including water, agriculture and land), and climate, as well as prospects for achieving the Paris Agreement’s short-term targets (as defined by Nationally Determined Contributions, or NDCs) and long-term goals of keeping the increase in the average global temperature below 2°C or even 1.5°C.
Here we summarize the key findings of this report based on our modeled projections under three increasingly ambitious greenhouse gas (GHG) emission-reduction scenarios: Paris Forever, Paris 2°C and Accelerated Actions. In broad terms, these scenarios correspond to maintaining existing climate policies in perpetuity, and capping global warming at 2°C and 1.5°C, respectively, by 2100. Most of our projections cover the 2020–2050 period, but some extend to 2100 and 2150. Finally, the findings shown are largely at the global level; regional detail is provided in sections corresponding to each category and can be further explored through our Outlook online tables (above) and visualization tool.
Population and economic growth are projected to lead to continued increases in energy needs and further electrification. Successful achievement of the Paris Agreement pledges will begin a shift away from fossil fuels, but additional actions are required to accelerate decarbonization.
Global Primary Energy
- Global primary energy use in the Paris Forever scenario grows to about 770 exajoules (EJ) by 2050, up by 31% from about 590 EJ in 2020. The share of fossil fuels drops from the current 80% to 70% in 2050. All energy types except coal grow from 2020 to 2050, led by non-biomass renewable energy (wind and solar) with more than a 5.6-fold increase. Natural gas consumption increases by about 50%, hydropower grows by 28% and oil use by 14%. Both nuclear and bioenergy increase by about 3%, while global coal consumption decreases by 7%. Coal’s share of primary energy declines from about 26% in 2020 to 18% in 2050.
- In the Paris 2°C scenario, global energy use peaks in 2040 at about 660 EJ and then declines to about 635 EJ by 2050. Wind and solar energy grow almost 9 times by 2050 relative to 2020, and natural gas use expands by 25%. Hydropower, bioenergy and nuclear power have similar growth rates as in the Paris Forever scenario. In contrast, oil use declines by 40% and coal use by 55% from 2020 to 2050. Coal’s share of global primary energy is reduced to 10% in 2050.
- The Paris Agreement pledges made by countries for the year 2030 do not substantially decrease the share of fossil fuels in global primary energy use. From about 80% in 2019, it declines to 74% in 2030. After 2030 it continues to decline, but even by 2050, a majority of global energy comes from fossil fuels in both Paris Forever and Paris 2°C scenarios. From 2020 to 2050, Covid-19 impacts on energy use and renewable energy deployment are relatively modest (2–4% reduction in energy use each year and virtually the same pathway for renewables relative to the non-Covid trajectory).
- Our projections show energy-intensity improvements from 2020 to 2050 in all economies. Global energy intensity in the Paris Forever scenario is projected to improve at an average annual rate of 2.3% between 2020 and 2050. In the Paris 2°C scenario, we project a 2.9% per year improvement during the same periods.
Private Vehicles and Transportation
- From about 10 million electric vehicles (EVs) in 2020, EV stock in the Paris Forever scenario reaches 100 million EVs in 2030, almost 300 million in 2040 and nearly 650 million in 2050. With the light-duty vehicle (LDV) stock increasing overall from 1.1 billion in 2020 to about 1.7 billion in 2050, the EV share of the LDV fleet reaches 38% in 2050. EV growth is even faster in the Paris 2°C scenario, with a projected 825 million EVs on the road by 2050, comprising 50% of the LDV fleet.
- In the Accelerated Actions scenario, the EV stock reaches more than 200 million vehicles in 2030, 600 million in 2040, and more than one billion in 2050. Assuming this accelerated deployment of EVs, two-thirds of all global LDVs by 2050 are electric. Our modeling implies that in achieving a 67% electrification of the global LDV stock, global EV sales would exceed 30 million in 2030, 60 million in 2040, and 100 million in 2050.
- The leaders in EV deployment in all scenarios are China, Europe and USA.
- Covid-19 decreases global electricity use. In comparison to a world without Covid, our modeling shows about a 4% Covid-induced reduction in electricity production in 2020–2030 and 3% reduction in 2035–2050.
- In the Paris Forever scenario, global electricity production (and use) grows by 67% from 2020 to 2050. In comparison to primary energy growth of 31% over the same period, electricity grows twice as fast, resulting in a continuing electrification of the global economy. Generation from variable renewables exhibit the fastest growth, with a 6-fold increase between 2020 and 2050.
- In the Paris 2°C scenario, global electricity production grows even faster, rising by 69% between 2020 and 2050. Policies after 2030 lead to a larger growth in variable renewables, which increase 9.7 times from 2020 to 2050.
- Electricity generation from renewable sources becomes a dominant source of power by 2050 in all scenarios. However, intermittency issues are not fully resolved in any region within that time frame, leading to a relatively large share of natural gas in generation.
- In the Paris Forever scenario, the oil price increases by 15% from 2020 to 2050, reaching $67/barrel. In the Paris 2°C scenario, this upward trend is reversed by a decrease in oil demand after 2030. The oil price rises to $64/barrel by 2030 and then declines to $45/barrel in 2050. Natural gas prices vary by region—rising with increased demand for replacing coal-based power generation, falling when renewables expand significantly. Coal prices also vary by region: prices decline in most regions due to reductions in demand for coal, with China a notable exception.
- The average global electricity price increases from 2020 to 2050 by 16% in the Paris Forever scenario and by 26% in the Paris 2°C scenario. Price increases are mostly driven by policy requirements to include more low-carbon generation options.
Emissions and Climate
It is widely recognized that the near-term Paris pledges are inadequate by themselves to stabilize climate. On the assumption that Paris pledges are met and retained in the post-2030 period without further emissions‑reduction efforts, future emissions growth will come from the Other G20 and developing countries, accelerating changes in global and regional temperatures.
- Covid-19 impacts on global GHG emissions persist but diminish over time—a 2% reduction by 2025 and about 1% in 2030–2040 below what they would be in a non-Covid world. After that, the difference imposed by the pandemic is less than 1%.
- Global GHG emissions in the Paris Forever scenario initially decrease from about 48 gigatonnes of CO2-equivalent (Gt CO2e) in 2020 to about 47.5 Gt CO2e in 2030, and then gradually increase to about 51 Gt CO2e in 2050 due to growth in countries with less stringent emissions targets. In the Paris 2°C scenario, GHG emissions follow the same path as in Paris Forever until 2030, and then more aggressive policies reduce them to 34 Gt CO2e by 2050. In the Accelerated Actions scenario, global GHG emissions decline to 20 Gt CO2e by 2050. Collectively, the world reduces its GHG emissions by almost 60% in 2050 relative to 2020 in that case.
- Extending our projections to 2150, global GHG emissions in the Paris Forever scenario continue their gradual increase after 2050 due to global population and GDP growth. Global emissions in the Paris 2°C scenario decline to about 10 Gt CO2e by 2100 and then remain at that level. Two scenarios that stabilize global average surface temperature at 1.5°C relative to pre-industrial levels show emissions starting to decrease in the 2020s. Global GHG emissions in these scenarios decline to about 8 Gt CO2e by 2100 and then remain at that level. We also tested a scenario where net GHG emissions are set to zero after 2070.
- Carbon dioxide (CO2) concentrations in the Paris Forever scenario continue to rise throughout (and after) the 21st century. By the beginning of the 2040s, the entirety of the Integrated Global System Modeling (IGSM) framework ensemble projection rises above 450 ppm of global CO2 concentrations. In addition, by mid-22nd century, more than half of the IGSM ensemble runs (i.e., at least 50% probability) show CO2 concentration at double their current level. Also by that time, we project with 100% likelihood that CO2e concentrations will rise to at least double the current level.
- In terms of radiative forcing of climate, our Paris Forever scenario aligns with the Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathway (RCP) 6.0 scenario, in that a radiative forcing of 6.0 W/m2 is attained at 2100. However, in the Paris Forever scenario there are no indications of climate-forcing stabilization (as in the RCP6.0 scenario). However, we find no likelihood of exceeding a radiative forcing of greater than 8.5 W/m2 (RCP 8.5) by mid-22nd century.
- By 2065, more than half of the IGSM ensemble’s Paris Forever projections exceed 2°C global climate warming, a fraction that rises to more than 75% by 2071 and more than 95% by 2085. By 2100, 95% of the IGSM projections indicate a global climate warming of at least 2.25°C, and the central tendency (i.e., median) of the projected warming is 2.8°C. All of the ensemble’s warming projections exceed 1.5°C warming after 2055. By mid-22nd century, the IGSM projections show that the world experiences at least a 3.3°C warming (in 95% of the IGSM ensemble runs) and most likely a warming of 4.1°C (median result).
- The MIT Earth System Model’s (MESM’s) global hydrologic sensitivity ranges from 1.7–3.3% per °C. In the Paris Forever ensemble, the MESM’s projected increase in global precipitation between today and mid‑century is projected to most likely (i.e., median result) be 0.04 mm/day, approximately an additional 7,400 km3 (or nearly 2 quadrillion gallons) of water that will be delivered from the atmosphere each year, which exceeds the current estimate of global annual human water consumption (4,600 km3). By 2100, the total change in precipitation will most likely rise to 0.11 mm/day (or 21,200 km3/yr)—nearly triple that of the mid‑century change.
- In both the Paris 2°C and Paris 1.5°C scenarios, global temperature will continue to rise through the next two decades. By mid‑century, the Paris 1.5°C scenario’s global temperature will stabilize, while the Paris 2°C global temperature will continue to rise through the 2070s. The Paris 2°C scenario also indicates that even among all the plausible outcomes captured by the IGSM ensemble, there is no likelihood of even the “coolest” trajectories to remain below 1.5°C at the end of the century. On the other hand, the Paris 1.5°C ensemble scenario can virtually assure the world of remaining below 2°C of global-averaged warming.
- The Paris 2°C and Paris 1.5°C scenarios not only stabilize global precipitation increase (by 2060 in Paris 1.5°C, and by 2100 in Paris 2°C), but substantially reduce the magnitude and potential range of increases. Paris 2°C cuts the increases in half and Paris 1.5°C reduces them to almost a third of the Paris Forever global precipitation changes. The hydrologic sensitivity of total precipitation from heavy and extreme precipitation events can be 5–10 times that of global mean precipitation. Thus, any global increase in precipitation conveys amplified risk of flooding worldwide. Therefore, these aggressive mitigation scenarios convey considerable reduction in both flood risk and uncertainty in the proportion (and cost) of adaptive actions that would otherwise be required
Water and agriculture are key sectors that will be shaped not only by increasing demands from population and economic growth but also by the changing global environment. Climate change is likely to add to water stress and reduce agricultural productivity, but adaptation and agricultural development offer opportunities to overcome these challenges.
- Under the Paris Forever scenario by mid‑century, approximately 5.8 billion people worldwide will be exposed to shortfalls in water supply (societal stress) across the major river basins where they reside. In addition, 3.6 billion people will be living within basins exposed to environmental water stress, and 3.2 billion people will be exposed to both societal and environmental water-stressed conditions.
- With a global population projected to reach 9.7 billion by 2050, the Paris Forever scenario indicates that more than half of the world’s population will experience pressures to its water supply, and that 3 of every 10 people will live in basins experiencing compounding societal and environmental pressures on water resources.
- Population projections under combined water stress in all scenarios reveal that the most aggressive climate target (i.e., the 1.5°C scenario) can reduce approximately 60 million of the additional 680 million people projected to be living in water‑stressed basins in 2050 compared to today. Over half of the combined water-stress trend is the direct result of population increases across major river basins that are water-stressed under present-day climate conditions.
- While we observe a modest “co-benefit” of climate action to reducing the global extent of water stress, our results highlight that the majority of the expected increases in population under heightened water stress by mid‑century cannot be avoided or reduced by climate mitigation efforts alone.
- Under the Paris Forever scenario, overall food production increases by 90% from 2020 to 2050, crop production by 70% and livestock production by 81%. Livestock production grows faster than crop production due to higher shares of protein-rich food in diets when income rises. Food production grows faster than livestock and crop production.
- Under the Paris Forever scenario, technological change and changing agricultural management practices result in greater yields, which prevent high increases in prices. By 2050 food prices are only 2% higher than in 2020. Crop prices rise a bit more (7%), while livestock prices rise by 42% and forest products by 33%.
- Under the Paris 2°C scenario, the value of crop output is 1.5% lower than in the Paris Forever scenario, while livestock output reduces by 1.9% and food output by 2.3%. Changes in prices are also quite modest, but a bit more discernable than changes in output. Prices of livestock products initially increase, declining later by 4% by 2050 compared to the Paris Forever scenario, while prices of food products and crop products decrease by 5.4% and 2.8% respectively.
- Global land-use projections from 2020 to 2050 are quite stable. Natural forest areas decrease by 1% and natural grasslands by 3%. These are converted mostly to cropland areas, which increase by 7%, while pasture lands increase by only 0.14%.
- Acreage dedicated to biomass for energy increases by 38%, but as it occupies only 2.9% of the total cropland area in 2020, it remains relatively small in 2050 (3.7% of the total cropland area). By 2100, cropland area is only 2.3% larger than in 2020, while pasture land is 0.44% larger. Natural forests and natural grasslands decrease by 2% and 4% by 2100, respectively. Biomass area increases by 126% compared to the 2020 area to cope with the growth of bioenergy output, but the total biomass area covers only 6% of total cropland.
- Land-use changes in the Paris 2°C scenario are similar to those in the Paris Forever scenario by 2050, but quite different by 2100. By that time, the area dedicated to bioenergy output reaches 17% of total cropland area, while it is only 6% in the Paris Forever scenario. Cropland area increases by 22%, while pastureland decreases by 31% to give room for cropland and bioenergy expansion.
Meeting Short-Term Paris Commitments
Key countries and regions are progressing in fulfilling their Paris pledges. Many countries have declared more ambitious GHG emissions mitigation goals, while financing to assist the least developed countries in sustainable development is not forthcoming at the levels needed.
- In its 2020 Emissions Gap Report, the UN Environmental Program (UNEP) evaluated the emissions control packages of the G20 nations, grading each for adequacy. Thirteen of the 20 were projected to meet their NDCs with currently implemented policies, which collectively account for around 60% of 2020 GHG emissions. Five, including the U.S., were judged to need additional measures, and insufficient information was available to evaluate the remaining two.
- Our estimate of economic growth to 2030 and beyond, compared to the pre-pandemic projection show that Covid-19’s GDP impact will, for many nations, lower the economic cost of the measures required to fulfill their NDCs. Taken all together, microeconomic effects of Covid-19 appear to further ease the burden of meeting existing Paris pledges.
- Harder to judge is the effect of the current economic downturn and associated political disruption on the priority nations will give to the climate threat and their Paris pledges. Also unknown is what will happen to next steps in implementation of the Paris Agreement. On the other hand, there are encouraging signs of commitment by several of the largest greenhouse gas emitters.
- Accounting for the pandemic’s effect on economic growth and assuming all nations meet their NDCs under these conditions, the result is stabilization of global GHG emissions through 2030. With the prospect that Covid-19’s effects may lower the effort required to meet existing pledges, and the announced increase in ambition by several large emitters, it is likely that the world’s collective efforts will not only achieve this level of emissions control by 2030, but exceed it.
Long-Term Climate Stabilization Goals
The Paris Agreement established more precise long-term temperature targets than previous climate pacts by specifying the need to keep “aggregate emissions pathways consistent with holding the increase in global average temperature well below 2°C above preindustrial levels” and further adding the goal of “pursuing efforts to limit the temperature increase to 1.5°C.” We find that those targets remain achievable, but in general require much deeper near-term reductions than those embodied in the NDCs agreed upon in Paris.