A Roadmap for Responding to Climate Change

April 2021

© 2021 MIT Alumni for Climate Action

Executive Summary

Human activities have added more than 1.5 trillion metric tons of carbon dioxide to Earth’s atmosphere since the pre-industrial period, increasing its concentration from below 300 parts per million (ppm) to over 415 ppm today, and projected to surpass 1,000 ppm before 2100 without effective action. This anthropogenic change is primarily due to burning fossil fuels, which has resulted in the observable and ongoing climate change, including global temperature rise, warming oceans, melting polar ice, glacial retreat, sea level rise, and increased extreme-weather events.  Ocean acidification is another significant global change attributed to increased carbon dioxide levels.

The United Nations Intergovernmental Panel on Climate Change (UN IPCC) assessments have detailed the wide-ranging damages from climate change and the far-reaching and unprecedented interventions required to limit them. In 2016, the UN Framework Convention on Climate Change (FCCC) including 196 of the world’s nations committed to reducing greenhouse gases through the Paris Agreement. It is imperative that these commitments be adhered to and enhanced in the next three decades to avoid irreversible damages to Earth’s natural cycles and ecosystems and to mitigate the threat to human societies.

The adverse impacts of anthropogenic climate change have significant social costs, which will increase dramatically if immediate action is not taken. These costs include economic damages from severe weather events and adverse health effects from pollutants generated by burning fossil fuels. Without immediate action, the projected costs are expected to become so severe as to threaten the security and well being of large numbers of people around the globe, ultimately leading to the loss of habitable land. A billion or more people are projected to be impacted in the next 50 years.

Immediate actions that are necessary to avoid the worst damages include termination of fossil fuel uses and their rapid replacement with carbon-neutral energy sources.  Transition to renewable solar and wind energy which are now economically competitive, and electrification of building and industrial thermal energy systems are key priorities. In addition, improvements in energy efficiency and reductions in energy use are urgently needed. Concurrently, careful management of carbon sequestration assets such as coastal marshes, tropical forests and agricultural lands is essential. In order to achieve the aspirational goal of net-zero greenhouse gas emissions by 2050 or earlier, investments in research and development of all promising technologies are urgently needed. As capture technologies become economically viable, they might support reductions below net-zero in the future.

An aggressive timeline is essential to avoid the worst damages from climate change that will otherwise result in the coming decades of the 21st century. Such damages include increasingly more frequent and destructive weather events, food and water insecurity, and loss of habitats for large human populations. Urgent responses and actions are needed at the national, regional, and local levels as well as by institutional and individual leaders and citizens.

Summary Recommendations

Central to our response to climate change is a pledge to reduce and eliminate fossil fuel use as rapidly as possible in order to stay within the limits set by the Paris Agreement. We need an aggressive timeline to avoid the worst climate change damages, which will otherwise occur during the 21st century. In addition, we must adapt to the changes already underway and develop the technologies needed to achieve carbon-neutrality. The following are priorities and actions to effectively address the challenges of climate change:

Enact Net-zero or Carbon-neutral Legislation. “Carbon-neutral” means no net addition of greenhouse gases in the atmosphere. The sooner we can achieve this aspirational goal, the less damage we will experience in the future. Decisive leadership is required on national, international, and regional levels. In addition to decisive action from our elected leaders, collaboration of ordinary citizens and businesses is needed. We must commit to cut greenhouse gases by 50% by 2030 and become carbon neutral by 2050 through legislation and deed.


Replace Fossil Fuels with Carbon-free Energy. The pathway to the net-zero target begins by replacing power from fossil-fuel plants with renewable wind and solar power, and rapidly expanding  off-shore wind power capability and solar photovoltaic capability. On-shore wind power and solar installations need to be expanded through incentivizing these technologies and eliminating subsidies to fossil fuel plants and fossil fuel producers. Construction of new coal-fired power should be banned in the US and worldwide. As energy production moves towards greener, renewable sources, the infrastructure supporting energy production and storage should be developed.

Electrify and Decarbonize Transportation Systems. Expand and expedite the transition to electric-powered and zero-carbon-fuel vehicles for all weight classes of on-road cars, trucks and buses. The same technologies can be implemented in off-road, industrial and many marine and heavy equipment applications. Any remaining non-electric light rail should be electrified. Longer-haul rail can be electrified and/or use low-carbon biofuels/zero-carbon fuels. In aviation, development should be accelerated for hybrid and electric aircraft. Longer-distance aircraft can migrate to lower-carbon biofuels/zero-carbon fuels. Ready access to the appropriate vehicle energy source will be critical to widespread adoption.

Improve Buildings and Communities. Conversion of all building energy systems to zero carbon is already economically available and should be aggressively implemented. All building energy systems must undergo full and efficient electrification and building codes need to include cradle-to-grave carbon emission guidelines. Financial incentives and public outreach should be used to encourage building owners to increase energy efficiency. City planning must take a holistic and long-term approach. Simulation software is available to help in designing living, walkable communities. For densely populated areas that often include commercial and industrial spaces, increased implementation of district energy is highly recommended.

Reform Land Management and Agricultural Practices. With increases in global population, careful management of land use and agricultural practices is essential. The most critical needs are to reduce conversion of tropical land for beef and oilseed production. Developed countries must provide resources and leadership to help offset the burdens to less-developed countries, as well as help provide solutions to land management and farming challenges. Potential solutions include improved practices that maintain soil health (regenerative agriculture) and and provide sustainable agricultural efficiency, use of ecologically beneficial alternatives to industrial fertilizers, and managed grazing, as well as exploring new approaches that integrate trees and farming, such as agroforestry and silvopasture. Tropical countries relying primarily on agriculture for their economies will require assistance to employ and feed their populations and be assured of fair income from agricultural exports.

Achieving Net Zero: Carbon Capture and Sequestration. Annual negative emissions are required to achieve carbon neutrality by 2050. Some portion of the negative emissions capacity can be generated through  improvements to management of agricultural and forest lands to increase their capacity for carbon capture, which will also improve air and water quality, thereby promoting better health. Significant advances are also needed for carbon capture and storage technology. R&D will be needed to select the best set of capture and storage technologies with the most promise for economies of scale, and ultimately the lowest cost for CO2 removal when implemented at scale.

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