Charting the Earth's Future
The 2023 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 last (2021) 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 what’s needed to accelerate innovation in climate mitigation and adaptation. 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 an emissions pathway consistent with the latter goal.
About the 2023 Outlook
The 2023 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 two scenarios: Current Trends and Accelerated Actions. In broad terms, these scenarios correspond to either preserving existing climate policies or capping global warming at 1.5°C by 2100. More precise scenario definitions are presented in “Drivers of Global Change” on page 7. Most of our projections cover the 2020-2050 period, but some extend to 2100 and 2150. Finally, the findings shown below 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 Current Trends scenario grows to about 650 exajoules (EJ) by 2050, up by 15% from about 560 EJ in 2020. The share of fossil fuels drops from the current 80% to 70% in 2050. Variable renewable energy (wind and solar) is the fastest growing energy source with more than an 8.6-fold increase in 30 years.
- In the Accelerated Actions scenario, global primary energy consumption declines after 2025 due to price- and policy-driven energy-efficiency measures, and reaches about 430 EJ in 2050. The share of low-carbon energy sources grows from 20% in 2020 to slightly more than 60% in 2050, a much faster growth rate than in the Current Trends scenario. Wind and solar energy in the Accelerated Actions scenario undergo more than a 13.3-fold increase.
- Our projections show energy-intensity improvements from 2020 to 2050 in all economies. During this period, global energy intensity is projected to improve at an average annual rate of 2% in the Current Trends scenario, and 3.1% in the Accelerated Actions scenario.
- In the Current Trends scenario, global electricity production (and use) grows by 73% from 2020 to 2050. In comparison to primary energy growth of 15% over the same period, electricity consumption grows much faster, resulting in a continuing electrification of the global economy. Generation from variable renewables exhibits the fastest growth (see Global Primary Energy, above).
- In the Accelerated Actions scenario, global electricity production grows even faster, rising by 87% between 2020 and 2050. More ambitious climate policies lead to a larger growth in variable renewables (See Global Primary Energy, above).
- Electricity generation from renewable sources becomes a dominant source of power by 2050 in both scenarios that we consider. To ensure a transition to low-carbon power generation in less economically developed regions, rich countries must provide sufficient technology transfer and financial support to incentivize further decarbonization.
- In the Current Trends scenario, our modeling projects a rather stable crude oil price, with a five-year average of around $75/barrel. Global oil consumption also remains fairly stable. In the Accelerated Actions scenario, this trend is changed by a decrease in oil demand after 2030.
- The oil price declines from about $75/barrel by 2025 to $60/barrel in 2050, a 20% reduction. In this scenario, global oil consumption drops from about 190 EJ in 2025 to about 105 EJ 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.
- The average global electricity price increases from 2020 to 2050 by 20% in the Current Trends scenario and by 40% in the Accelerated Actions scenario. Price increases are mostly driven by policy requirements to include more low-carbon generation options.
Scaling Up Low-Carbon Solutions
- Due to a sizeable need for hydrocarbons in the form of liquid and gaseous fuels for sectors such as heavy-duty long-distance transport, high-temperature industrial heat, agriculture, and chemical production, hydrogen-based fuels and renewable natural gas remain attractive options, but the challenges related to their scaling opportunities and costs must be resolved.
- The scenarios considered in this Outlook may be affected by the pace of technological development in existing low-carbon technologies, such as wind and solar (and energy storage technologies to address their intermittency). To realize their potential, challenges related to permitting areas for generation and transmission lines, as well as materials and critical minerals availability, should be addressed. A more proactive consumer acceptance of low-carbon lifestyles may contribute to a move towards a circular economy. To reduce the need for materials, demand-side management needs to be accelerated.
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 with further emissions reduction efforts, future emissions growth will likely come from developing countries, accelerating changes in global and regional temperatures.
- Global GHG emissions in the Current Trends scenario stay relatively constant, initially increasing from about 47 gigatonnes of CO2equivalent (Gt CO2e) in 2020 to about 48 Gt CO2e in 2030, and then gradually decreasing to about 45 Gt CO2e in 2050 due to policies in countries with more stringent emissions targets. In the Accelerated Actions scenario, global GHG emissions follow the same path as in the Current Trends scenario until 2025, and then more aggressive policies reduce them to 18 Gt CO2e by 2050, a 62% decrease relative to 2020.
- Extending our projections to 2150, global CO2 emissions in the Current Trends scenario remain relatively flat at about 30 Gt CO2e, reflecting mild policies on energy and industrial emissions. Moreover, our global GHG emissions projection shows a gradual increase in agriculture-related CH4 and N2O due to global population and GDP growth. In the Accelerated Actions scenario, global GHG emissions start to decrease after 2025. Global CO2 emissions approach zero in the second half of the century, but non-CO2 GHGs such as CH4 and N2O are still not fully eliminated because of agriculture-related activities.
- Carbon dioxide (CO2) concentrations in the Current Trends 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 concentration. In addition, by mid-22nd century, more than half of the IGSM ensemble runs (i.e., at least 50% probability) show CO2 concentrations at double their current level. Also by that time, we project with nearly 75% likelihood that CO2e concentrations will rise to at least double the current level.
- In terms of radiative forcing of climate, our Current Trends scenario is most closely consistent 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 almost attained in 2100. However, the Current Trends scenario shows 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 (as in the IPCC RCP 8.5 scenario) by mid-22nd century.
- By 2060, more than half of the IGSM ensemble’s Current Trends projections exceed 2˚C global climate warming, a figure that rises to more than 75% by 2070 and more than 95% by 2090. By 2100, 95% of the IGSM projections indicate a global climate warming of at least 2.2˚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 2050. By mid-22nd century, the Current Trends projections show that the world experiences at least a 2.9˚C warming (95% of the IGSM ensemble warmer) and most likely a warming of 3.8˚C (median result). The strongest global climate warming indicated by our projections (95th percentile) would be 4.6˚C.
- Our latest climate-model information indicates that maximum temperatures will likely outpace mean temperature trends over much of North and South America, Europe, northern and southeast Asia, and southern parts of Africa and Australasia. So as human-forced climate warming intensifies, these regions are expected to experience more pronounced record-breaking extreme heat events.
- The MESM’s global hydrologic sensitivity ranges from 1.7–3.3%/˚C. In the Accelerated Actions ensemble, MESM’s projected increase in global precipitation between today and mid-century is most likely (i.e., median result) to 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 the Accelerated Actions scenario, global temperature will continue to rise through the next two decades. By mid-century, global temperature will stabilize, and then slightly decline through the latter half of the century. By the end of the century, the Accelerated Actions ensemble scenario indicates that the world can be virtually assured of remaining below 2˚C of global-averaged warming.
- The Accelerated Actions scenario not only stabilizes global precipitation increase (by 2060), but substantially reduces the magnitude and potential range of increases to almost a third of the Current Trends global precipitation changes. Further evidence indicates that the hydrologic sensitivity of 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 reductions in flood risk as well as 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 Current Trends 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, 3.75 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 Current Trends 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 water basins where the compounding societal and environmental pressures on water resources will be experienced.
- Population projections under combined water stress in all scenarios reveal that the Accelerated Actions scenario can reduce by approximately 40 million the additional 570 million people living in water-stressed basins at mid-century. More than 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 find 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 Current Trends scenario, the value of the overall food production increases by 90% from 2020 to 2050, crop production by 70% and livestock production by 61%. Food production grows faster than livestock and crop production, and populations trends are a key driver.
- Under the Current Trends scenario, greater agricultural yields will prevent high increases in prices. By 2050 food prices are only 1% higher than in 2020. Crop prices grow a bit faster (10%), while livestock prices rise by 26%.
- Under the Accelerated Actions scenario, the value of crop output at mid-century is 5% lower than in the Current Trends scenario, while the value of livestock output reduces by 9% and food output by 5%. Changes in prices are also quite modest, but most salient in livestock. By mid-century, prices of livestock products are highly impacted under Accelerated Actions, increasing by 26% from Current Trends, while prices of food products and crop products increase by about 3% and 2% respectively.
- Global land-use projections from 2020 to 2050 are quite stable. Natural forest areas decrease by 1.4% and natural grasslands by 3%. These are converted mostly to cropland areas, which increase by 7.5%, while pasture lands increase by only 1.8%.
- In the Current Trends scenario, acreage dedicated to biomass for energy increases by up to 46% by mid-century, but as it occupies only 3% of the total cropland area in 2020, it remains relatively small in 2050 (4% of the total cropland area).
- Very different dynamics distinguish changes in agricultural land and natural areas around the world. The Rest of the World region faces larger land-use changes than other regions, due to stronger population and income growth. Cropland area increases by 14% by 2050.
- Pasture area decreases by 2.5% by 2050. On the other hand, cropland in India and China decreases by 1.7% in 2050, while land for bioenergy grows by 78%, covering 4.3% of the total cropland area.
- Land-use changes in the Accelerated Actions scenario are similar to those in the Current Trends scenario by 2050, except for land dedicated to bioenergy production. At the world level, the Accelerated Actions scenario requires cropland area to increase by 1% and pastureland to decrease by 4.2%, but land use for bioenergy must increase by 44%.
Meeting Short-Term Paris Commitments
Numerous countries and regions are progressing in fulfilling their Paris Agreement 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 the Global Stocktake Synthesis Report, the U.N. Framework Convention on Climate Change (UNFCCC) evaluated emissions reductions communicated by the parties of the Paris Agreement and concluded that global emissions are not on track to fulfill the most ambitious long-term global temperature goal of the Paris Agreement (to limit warming to 1.5 °C above pre-industrial levels), and there is a rapidly narrowing window to raise ambition and implement existing commitments in order to achieve that goal. Our Current Trends scenario arrives at the same conclusion.
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 they require much deeper near-term reductions than those embodied in the NDCs agreed upon in Paris.