Top 10 Solutions to Reverse Climate Change

Image: Windmills by Dmitry Anikin. Topic: clean energy is one way to reverse climate change
Windmills by Dmitry Anikin

Paul Hawken and the Project Drawdown experts thought they knew what to expect when they modeled and ranked 80 solutions that could reverse climate change. But the data had some surprises in store. 

Most prominently was that even when the solutions are modeled in terms of what they call a “Plausible Scenario”—a conservative measure of projected solution implementation that is “reasonable yet optimistic”—society still makes great strides toward achieving drawdown, the point where greenhouse-gas levels in the atmosphere begin to decline. 

Together, all 80 reduce or sequester carbon by 1,051 gigatons by 2050 in the Plausible Scenario. Using the scenario that gets us to drawdown—which requires ramping up the solutions a bit more than the conservative measure, particularly renewable energy—they reduce or sequester carbon by 1,442 gigatons by 2050. 

Below are the top ten solutions, ranked in terms of emissions reduction potential over a 30-year period. For the other 90 solutions, we highly recommend you read Drawdown: the Most Comprehensive Plan Ever Proposed to Reverse Global Warming (Penguin Books, 2017), edited by Paul Hawken. —the Green America editors 

Top 10 Solutions to Reverse Climate Change

1. Refrigerant Management

Tell Walmart to eliminate HFCs

The problem: Every refrigerator, supermarket case, and air conditioner contains chemical refrigerants that absorb and release heat, making it possible to chill food and keep buildings and vehicles cool. Refrigerants, specifically chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), were once key culprits in depleting the stratospheric ozone layer, which is essential for absorbing the sun’s ultraviolet radiation. Thanks to the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer, CFCs and HCFCs have been phased out of use.

It took two short years from the discovery of the gaping hole over the Antarctic for the global community to adopt a legally mandated course of action. Now, three decades later, the ozone layer is beginning to heal. 

Refrigerants continue to cause climate change, however. Huge volumes of CFCs and HCFCs remain in circulation, retaining their potential for ozone damage. Their replacement chemicals, primarily hydrofluorocarbons (HFCs), have minimal deleterious effect on the ozone layer, but their capacity to warm the atmosphere is 1,000 to 9,000 times greater than that of carbon dioxide, depending on their exact chemical composition.

Solutions in progress: In October 2016, officials from more than 170 countries gathered in Kigali, Rwanda, to negotiate a deal to address the problem of HFCs. Despite challenging global politics, they reached a remarkable agreement. Through an amendment to the Montreal Protocol, the world will begin phasing HFCs out of use, starting with high-income countries in 2019 and then expanding to low-income countries—some in 2024, others in 2028. HFC substitutes are already on the market, including natural refrigerants such as propane and ammonia. Unlike the Paris Climate Agreement, the Kigali deal is mandatory, with specific targets and timetables.

Work to be done: The process of phasing out HFCs will unfold over many years, and they will persist in kitchens and condensing units in the meantime. According to the Lawrence Berkeley National Laboratory, 700 million air conditioning units will have come online worldwide by 2030. 

Refrigerants currently cause emissions throughout their life cycles, but 90 percent of emissions happen at disposal. After being carefully removed and stored, refrigerants can be purified for reuse or transformed into other chemicals that do not cause warming. 

The Kigali Accord ensures a step change is coming, and other practices focused on existing stocks could reduce HFC emissions further.

Green America resources: Green America's Cool It! Campaign urges supermarkets to curb their extremely harmful HFC use, starting with the biggest offender: Walmart. You can also get tips on reducing your need for air conditioning and saving energy at home in our article,“Ten Easiest Ways to Cut Your Energy Use in Half.”


Project Drawdown analysis includes emissions reductions that can be achieved through the management and destruction of refrigerants already in circulation.

Greenhouse gas (GHG) reduction (Plausible Scenario): 89.74 gigatons (GT) of reduced CO2-equivalent (CO2-e—the common measure for all greenhouse gases) by 2050.

GHG reduction (Drawdown Scenario—requires greater refrigerant management): 96.49 gigatons of reduced CO2-e by 2050.

Cost (Plausible Scenario): Data too variable to be determined.

Savings (Plausible Scenario): The costs to establish and operate recovery, destruction, and leak avoidance outweigh the financial benefit: –$902.8 billion net savings.

2. Wind Turbines (Onshore) 

The problem: Fossil fuels sidelined zero-emission wind energy during the mid-twentieth century. Wind energy has its challenges. The weather is not the same everywhere. The variable nature of wind means there are times when turbines are not turning. Critics argue that turbines are noisy, aesthetically unpleasant, and at times deadly to bats and migrating birds.

Another impediment to wind power is inequitable government subsidies. The International Monetary Fund estimates that the fossil-fuel industry received more than $5.3 trillion worldwide in direct and indirect subsidies in 2015. In comparison, the US wind-energy industry has received $12.3 billion in direct subsidies since 2000.  

Solutions in progress: Today, 314,000 wind turbines supply 3.7 percent of global electricity. It will soon be much more. In 2015, a record 63 gigawatts of wind power were installed around the world, despite a dramatic drop in fossil-fuel prices. In many locales, wind is either competitive with or less expensive than coal-generated electricity.

In the US, the wind-energy potential of just three states—Kansas, North Dakota, and Texas—would be sufficient to meet electricity demand from coast to coast. 

Current technologies make it easier to overcome fluctuations in supply and demand. Interconnected grids can shuttle power to where it is needed. Newer turbine designs address concerns over bird and bat deaths with slower-turning blades and siting practices to avoid migration paths.

Ongoing cost reductions will soon make wind energy the least expensive source of installed electricity capacity, perhaps within a decade.

Work to be done: The ways and means for the United States to be fossil-fuel- and energy-independent are here. What is often missing is political will and leadership to reverse climate change.

On the policy side, energy portfolio standards can mandate a share of renewable generation. Grants, loans, and tax incentives can encourage construction of more wind capacity and ongoing innovation. 

Wind energy is part of a system. Investment in energy storage, transmission infrastructure, and distributed generation is essential to its growth. For the world, the decision is simple: Invest in the future or in the past. 

Green America resources: Green America’s Divest/Invest campaign encourages people to divest from the top 200 fossil-fuel companies and reinvest in sustainability. 


An increase in onshore wind from 3 to 4 percent of world electricity use to 21.6 percent could result in:

GHG gas reduction (Plausible Scenario): 84.6 GT of reduced CO2 by 2050.

GHG reduction (Drawdown Scenario—requires greater wind-energy increase): 146.5 GT of reduced CO2 by 2050.

Cost (Plausible Scenario): $1.2 trillion, though costs are falling annually and could deliver more savings.

Savings (Plausible Scenario): Onshore wind turbines can deliver a net savings of $7.4 trillion over three decades of operation.

3. Reduced Food Waste 

The problem: A third of the food raised or prepared does not make it from farm or factory to fork. That number is startling, especially when paired with this one: Hunger is a condition of life for nearly 800 million people worldwide. And this one: The food we waste contributes 4.4 gigatons of CO2-equivalent into the atmosphere each year—roughly eight percent of total anthropogenic greenhouse-gas emissions.

In places where income is low and infrastructure is weak, food loss is typically unintended and structural in nature—bad roads, lack of refrigeration or storage facilities, poor equipment or packaging, a challenging combination of heat and humidity. Wastage occurs earlier in the supply chain, rotting on farms or spoiling during storage or distribution.

In regions of higher income, unintentional losses tend to be minimal; willful food waste dominates farther along the supply chain. Retailers reject food based on bumps, bruises, coloring—aesthetic objections of all sorts. Other times, they simply order or serve too much, lest they risk shortages or unhappy customers.

Similarly, consumers spurn imperfect spuds in the produce section, overestimate how many meals they will cook in a week, toss out milk that has not gone bad, or forget about leftover lasagna in the back of the fridge.

Basic laws of supply and demand also play a role. If a crop is unprofitable to harvest, it will be left in the field. And if a product is too expensive for consumers to purchase, it will idle in the storeroom. 

Regardless of the reason, the outcome is the same. Producing uneaten food squanders a whole host of resources—seeds, water, energy, land, fertilizer, hours of labor, financial capital—and generates greenhouse gases at every stage—including methane when organic matter lands in the global rubbish bin. 

Solutions in progress: The United Nations’ Sustainable Development Goals call for halving per capita global food waste at the retail and consumer levels by 2030, as well as reducing food losses along production and supply chains.

Work to be done: The interventions that can address key waste points in the food chain are numerous and varied. In lower-income countries, improving infrastructure for storage, processing, and transportation is essential. Strengthening communication and coordination between producers and buyers is also paramount for keeping food from falling through the cracks. Given the world’s many smallholder farmers, producer organizations can help with planning, logistics, and closing capacity gaps. In higher-income regions, major interventions are needed at the retail and consumer levels. Most important is to preempt food waste before it happens, for greatest reduction of upstream emissions, followed by reallocation of unwanted food. 

Standardizing date labeling on food packages is an essential step. Currently, “sell by” or “best before” dates and the like are largely unregulated designations, indicating when food should taste best. Though not focused on safety, these markers often confuse consumers about expiration. 

Education is another powerful tool, including campaigns celebrating “ugly” produce and public feasts made from nearly wasted food. National goals and policies can encourage widespread change, as well.

Green America resources: Get ideas from our “Tackling Food Waste” issue of the Green American.


If the world reduces its food waste by 2050, it would see the following:

GHG reduction (Plausible Scenario): 70.53 GT of reduced CO2-e by 2050.

GHG reduction (Drawdown Scenario—requires greater food waste reduction): 83.03 GT of reduced CO2-e by 2050..

Cost (Plausible Scenario): Too variable to be determined.

Savings (Plausible Scenario): Too variable to be determined.

4. Adoption of a Plant-Rich Diet 


A vegan dessert from Candle Cafe, a vegan, local, and organic restaurant in New York City that also offers frozen vegan meals and vegan cookbooks. Photo courtesy of Candle Cafe.

The problem: The Western diet comes with a steep price tag for climate change. The most conservative estimates suggest that raising livestock accounts for nearly 15 percent of global greenhouse gases emitted each year; the most comprehensive assessments of direct and indirect emissions say more than 50 percent.

Outside of innovative, carbon-sequestering managed-grazing practices described in another section of Drawdown, the production of meat and dairy contributes many more emissions than growing their sprouted counterparts—vegetables, fruits, grains, and legumes. 

Ruminants such as cows are the most prolific offenders, generating the potent greenhouse gas methane as they digest their food. In addition, agricultural land use and associated energy consumption to grow livestock feed produce carbon dioxide emissions, while manure and fertilizers emit nitrous oxide. If cattle were their own nation, they would be the world’s third-largest emitter of greenhouse gases.

Overconsumption of animal protein also comes at a steep cost to human health. Eating too much of it can lead to certain cancers, strokes, and heart disease. Increased morbidity and health care costs go hand in hand.

Solutions in progress: With billions of people dining multiple times a day, imagine how many opportunities exist to turn the tables. It is possible to eat well, in terms of both nutrition and pleasure, while eating lower on the food chain and thereby lowering emissions. 

Work to be done: A groundbreaking 2016 study from the University of Oxford modeled the climate, health, and economic benefits of a worldwide transition to plant-based diets between now and 2050. Business-as-usual emissions could be reduced by as much as 70 percent through adopting a vegan diet and 63 percent for a vegetarian diet (which includes cheese, milk, and eggs). The model also calculates a reduction in global mortality of six to ten percent. 

The case for a plant-rich diet is robust. That said, bringing about dietary change is not simple because eating is profoundly personal and cultural. For individuals to give up meat in favor of options lower on the food chain, those options should be available, visible, and tempting. 

Meat substitutes made from plants are a key way to minimize disruption of established ways of cooking and eating. Between rapidly improving products, research at top universities, venture-capital investment, and mounting consumer interest, experts expect markets for non-meats to grow rapidly. 

Beyond promoting “reducitarianism,” if not vegetarianism, it is also necessary to reframe meat as a delicacy, rather than a staple. First and foremost, that means ending price-distorting government subsidies, such as those benefiting the US livestock industry. Debunking protein myths and amplifying the health benefits of plant-rich diets can also encourage individuals to change their eating patterns.  

Green America resources: Read about how the world could eat less meat and the impacts it could have in our “Don’t Have a Cow” issue of the Green American.


If the world reduces its meat consumption by 2050, it would see the following:

GHG reduction (Plausible Scenario): 66.11 GT of reduced CO2-e by 2050.

GHG reduction (Drawdown Scenario—requires further reduction of meat consumption): 78.65 GT of reduced CO2-e by 2050.

Cost (Plausible Scenario): Too variable to be determined.

Savings (Plausible Scenario): Too variable to be determined.

5. Tropical Forest Restoration

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Sustainable forest management in Indonesia. At least 751 million acres of land in the tropics could be restored to intact forests, reducing 62.1 gigatons of CO2. Photo by Biosphoto via Alamy.

The problem: In recent decades, tropical forests—those located within 23.5 degrees north or south of the equator—have suffered extensive clearing, fragmentation, degradation, and depletion of flora and fauna. Once blanketing 12 percent of the world’s land masses, they now cover just five percent. 

When we lose forests, primarily to agricultural expansion or human settlement, carbon dioxide discharges into the atmosphere. Tropical forest loss alone is responsible for 16 to 19 percent of greenhouse-gas emissions caused by human activity. 

Solutions in progress: Restoration of tropical forests, both passive and intentional, is now a growing trend. As forest ecosystems come back to life, trees, soil, leaf litter, and other vegetation absorb and hold carbon, taking it out of global-warming rotation. 

In 2011, the Bonn Challenge set an ambitious target of restoring 370 million acres of forest worldwide by 2020. The 2014 New York Declaration on Forests affirmed that aim and added a cumulative target of 865 million acres restored globally by 2030. Should the world accomplish that goal, a total of 12 to 33 gigatons of CO2 would be removed from the atmosphere and become terrestrial once again. 

Work to be done: “More than 4.9 billion acres [of forests] worldwide offer opportunities for restoration—an area larger than South America,” a team of researchers from the World Resources Institute reports. Three-quarters of that land would be best suited to a “mosaic” forest-restoration approach, blending forests, trees, and agricultural land uses. Up to 1.2 billion acres are ripe for full restoration of large forests with dense canopy cover. The opportunities are enormous, and the majority of it lies in tropical regions. In a median time of 66 years, tropical forests can recover 90 percent of the biomass that old-growth landscapes contain.  

Given the interconnectedness of people and forests, a particular framework for restoration has emerged: forest landscape restoration. The approach, proposed by the United Nations Food and Agriculture Organization, means “regarding the landscape as an integrated whole ... looking at different land uses together, their connections, interactions, and a mosaic of [restoration] interventions.” 

It means there is no single formula for forest restoration. Making restoration a collaborative process can ensure it is done with and for local communities, and that root causes of forest damage are addressed.

The bulk of restoration opportunities lies primarily within low-income countries in tropical regions. Those countries cannot manage the level of investment required, nor should they, since the benefits of restoration provide value and a service to all. The relevant stakeholders are the entire human race, and some bear greater responsibility for the problem of climate change than others.

Because forest restoration is such a potent solution to climate change, commitments and funding need to be a global priority. And because restoration efforts have ranged from success to failure, we need to analyze why, scale best practices, and eliminate those that do not work.  Initiatives need to respect land rights and tenure, especially those of Indigenous people. 

Green America resources: Green America’s Skip the Slip campaign helps forests around the world by urging companies to shift away from using millions of pounds to unrecyclable paper receipts and use online receipts instead. In other sectors, Green America's campaigns work to protect our forests by moving towards recycled paper or online.


In theory, 751 million acres of degraded land in the tropics could be restored to continuous, intact forest. Project Drawdown’s Plausible Scenario assumes restoration could occur on 435 million acres, resulting in:

GHG reduction (Plausible Scenario): 61.2 GT of reduced CO2 by 2050.

GHG reduction (Drawdown Scenario—requires more restoration): 89 GT of reduced CO2 by 2050..

Cost (Plausible Scenario): Data too variable to be determined.

Savings (Plausible Scenario): Data too variable to be determined.

6. Educating Girls


Sunita was once forced to weave carpets and perform domestic work from 4 a.m. late into the night. Now, she attends school through GoodWeave’s education program. GoodWeave rescues child weavers from carpet looms in South Asia and invests in their education and rehabilitation. It also certifies carpets and looms as being free from child labor. Photo by U. Roberto Romano for Goodweave.

The problem: Today, more than 130 million girls are denied the fundamental right to attend school and lay a foundation for their lives. The situation is most dire in secondary classrooms.

Economic barriers include lack of family funds for school fees and uniforms, as well as prioritizing the more immediate benefits of having girls fetch water or firewood, or work a market stall or a plot of land. 

Cultural barriers encompass traditional beliefs that girls should tend the home rather than learn to read and write, should be married off at a young age, and, when resources are slim, should be skipped over so boys can be sent to school instead. 

Schools that are farther afield put girls at risk of gender-based violence on their way to and from, while other dangers and discomforts are present at school itself. Disability, pregnancy, childbirth, and female genital mutilation also can be obstacles. 

The education gap also matters for global warming. According to the Brookings Institution, “The difference between a woman with no years of schooling and with 12 years of schooling is almost four to five children per woman.” Women with more years of education have fewer, healthier children and actively manage their own reproductive health.  

In the poorest countries, per capita greenhouse-gas emissions are low. From one-tenth of a ton of carbon dioxide per person in Madagascar to 1.8 tons in India, per-capita emissions in lower-income countries are a fraction of the US rate of 18 tons per person per year. Nevertheless, changes in fertility rates in those countries would have multiple benefits for girls and women, families, communities, and society. 

Solution in progress: Nobel laureate and girls’ education activist Malala Yousafzai has famously said, “One child, one teacher, one book, and one pen can change the world.” An enormous body of evidence supports her conviction. For starters, educated girls realize higher wages and greater upward mobility, contributing to economic growth. Their rates of maternal mortality drop, as do mortality rates of their babies. They are less likely to marry as children or against their will. They have lower incidence of HIV/AIDS and malaria. Their agricultural plots are more productive and their families better nourished. They are more empowered at home, at work, and in society. 

Education is the most powerful lever available for breaking the cycle of intergenerational poverty, while mitigating emissions by curbing population growth. 

Education also shores up resilience to climate change impacts. For example, a 2013 study found that educating girls “is the single most important social and economic factor associated with a reduction in vulnerability to natural disasters.” This decreased vulnerability also extends to their children, families, and the elderly.

[Editor’s note: Increasing women’s involvement in the energy sector also leads to “more effective clean-energy initiatives, greater returns on investment in clean energy, and expanded emissions-reduction opportunities, according to the International Union for the Conservation of Nature.] 

Work to be done: In 2011, the journal Science published a demographic analysis of the impact of girls’ education on population growth. It details a “fast track” scenario, based on South Korea’s actual climb from one of the least to one of the most educated countries in the world. If all nations adopted a similar rate and achieved 100 percent enrollment of girls in primary and secondary school by 2050, there would be 843 million fewer people worldwide than if current enrollment rates sustain. 

The encyclopedic book What Works in Girls’ Education (Brookings Institution Press, 2015) maps out seven areas of interconnected interventions: 1) Make school affordable. 2) Help girls overcome health barriers. 3) Reduce the time and distance to get to school. 4) Make schools more girl-friendly. For example, offer child-care programs for mothers. 5) Improve school quality.  6) Increase community engagement. 7) Sustain girls’ education during emergencies. For example, establish schools in refugee camps. 

Green America resources: Green America’s Labor programs and End Smartphone Sweatshops campaign promote solutions that raise family income, get children out of factories and fields, and allow more children to go to school.


Because educating girls has an important impact on family planning (#7), Project Drawdown allocated 50 percent of total potential emissions reduction to each solution.

GHG reduction (Plausible Scenario): 59.6 GT of reduced CO2 by 2050.

GHG reduction (Drawdown Scenario—requires helping more girls attend school): 59.6 GT of reduced CO2 by 2050.

Cost (Plausible Scenario): By closing an annual financing gap of $39 billion, universal education in low- and lower-middle-income
countries could be achieved.

Savings (Plausible Scenario): The return on investing in girls is incalculable.

7. Family Planning

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Kenya has made significant gains in education, with more than 80 percent of all boys and girls currently enrolled in primary schools, and 50 percent of boys and girls in secondary schools, Poverty is the main reason for low enrollment, and boys receive priority for higher education when there are financial constraints.Courtesy of Project Drawdown.

The problem:  Securing the fundamental right to voluntary, high-quality family-planning services, so women can have children by choice rather than chance and can plan their family size and spacing, is a matter of autonomy, dignity, and, yes, climate change. 

225 million women in lower-income countries say they want the ability to choose whether and when to become pregnant but lack the necessary access to contraception—resulting in some 74 million unwanted pregnancies each year. The need persists in some high-income countries as well, including the US, where 45 percent of pregnancies are unintended.

Challenges to expanding access to family planning range from basic supply of affordable and culturally appropriate contraception to education about sex and reproduction; from faraway health centers to hostile attitudes of medical providers; from social and religious norms to sexual partners’ opposition to using birth control. 

Currently, the world faces a $5.3 billion funding shortfall for providing the access to reproductive health care that women say they want to have. After being silent on the topic of family planning for more than 25 years, the UN Intergovernmental Panel on Climate

Change included access to reproductive health services in its 2014 synthesis report and pointed to population growth as an important factor in greenhouse-gas concentrations. (See #6 for statistics on per capita emissions.) Growing evidence suggests that family planning has the additional benefit of building resilience—helping communities and countries better cope with and adapt to inevitable changes brought by climate change.  

Solutions in progress: The success stories in family planning are striking. Iran put a program into place in the early 1990s that has been touted as among the most successful such efforts in history. Completely voluntary, it involved religious leaders, educated the public, and provided free access to contraception. As a result, fertility rates halved in just one decade. 

In Bangladesh, average birth rates fell from six children in the 1980s to two now, as the door-to-door approach pioneered in the Matlab hospital spread across the country: female health workers providing basic care for women and children where they live. Family planning requires social reinforcement—for example, the radio and television soap operas now used in many places to shift perceptions of what is “normal” or “right.” 

Work to be done: Honoring the dignity of women and children through family planning is not about centralized governments forcing the birth rate down—or up through natalist policies. Nor is it about agencies or activists in rich countries, where emissions are highest, telling people elsewhere to stop having children. It is most essentially about freedom and opportunity for women and the recognition of basic human rights.

Currently, family-planning programs receive just one percent of all overseas development assistance. That number could double—a moral move that happens to have meaning for the planet. 

Green America resources: Green America’s Labor and Clean Electronics programs support solutions that help women earn their own incomes and determine their own futures. 


Because educating girls (#6) has an important impact on family planning, Project Drawdown allocated 50 percent of total potential
emissions reduction to each solution.

GHG reduction (Plausible Scenario): 59.6 GT of reduced CO2 by 2050.

GHG reduction (Drawdown Scenario—requires providing more women with family-planning access): 59.6 GT of reduced CO2 by 2050.

Cost & savings (Plausible Scenario): Inappropriate to monetize a human right.

8. Solar Farms

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OCI Solar Power’s 60-acre Alamo 3 solar farm in Converse, TX, generates 5.5 megawatts (AC) of power for nearly 1,240 homes. Courtesy of OCI Solar Power (

The problem: The era of fossil fuels is over, and the only question is when the new era of clean energy will be upon us. Solar photovoltaics are only two percent of the global electricity mix at present. 

Solutions in progress: Solar farms are large-scale arrays of hundreds, thousands, or hundreds of thousands, or, in some cases, millions of panels that achieve generating capacity in the tens or hundreds of megawatts. These solar farms operate at utility scale, more like conventional power plants in the amount of electricity they produce.

The first solar photovoltaic (PV) farms went up in the early 1980s. Now, these utility-scale installations account for 65 percent of additions to solar PV capacity around the world.

If Ukrainian officials have their way, Chernobyl, the site of a mass nuclear meltdown in 1986, will house a 1-gigawatt solar farm, which would be one of the world’s largest.

Public investment, tax incentives, technology evolution, and brute manufacturing force have chipped away at the cost of creating PV, bringing it down to 65 cents per watt today. The decline in price has always outpaced predictions, and drops will continue. Informed predictions about the cost and growth of solar PV indicate that it will soon become the least expensive energy in the world. It is already the fastest growing. 

Compared to rooftop solar, solar farms enjoy lower installation costs per watt, and their efficacy in translating sunlight into electricity is higher. When their panels rotate to make the most of the sun’s rays, generation can improve by 40 percent or more. 

Work to be done: No matter where solar panels are placed, they are subject to the diurnal and variable nature of solar radiation and its misalignment with electricity use, peaking midday while demand peaks a few hours later. That is why, as solar generation continues to grow, so should complementary renewables that are constant, such as geothermal, and that have rhythms different from the sun, such as wind, which tends to pick up at night.

Energy storage and more flexible grids that can manage the variability of production from PV farms will also be integral to solar’s success.

The International Renewable Energy Agency already credits 220 million to 330 million tons of annual CO2 savings to solar PV. Could solar rise from two percent of the global electricity mix to meet 20 percent of global energy needs by 2027, as some University of Oxford researchers calculate? Thanks to complementary government interventions and market progress, there are many promising signs. 

Green America resources: Green America’s Solar Catalyst and Solar Circle programs have played a major role in accelerating solar in the US and abroad. Our new campaigns put pressure on AT&T, Verizon, and Amazon to power their massive servers with clean energy.  


Utility-scale solar is currently 0.4 percent of global electricity generation. Project Drawdown assumes it will grow to ten percent.

GHG reduction (Plausible Scenario): 36.9 GT of reduced CO2 by 2050.

GHG reduction (Drawdown Scenario—assumes higher growth): 64.6 GT of reduced CO2 by 2050.

Cost (Plausible Scenario): –$80.6 billion. (Solar farms are cheaper to install than fossil-fuel alternatives, so there’s actually a
savings on implementation.)

Savings (Plausible Scenario): $5.02 trillion in net savings.

9. Silvopasture

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A silvopasture field in Sweden, combining pastureland with climate-cooling trees. Photo by Bo Jansson (Alamy).

The problem: In Brazil and elsewhere, headlines condemn ranching as a driver of mass deforestation and attendant climate change. Cattle and other ruminants require 30 to 45 percent of the world’s arable land, and livestock produce roughly one-fifth of greenhouse gas emissions. 

Solutions in progress: Conventional wisdom says cows and trees do not belong together. The practice of silvopasture challenges this assumption of mutual exclusivity and could help shape a new era for the acreage dedicated to livestock and their food. 

From the Latin for “forest” and “grazing,” silvopasture is just that: the integration of trees and pasture or forage into a single system for raising livestock, from cattle and sheep to deer and ducks. Rather than seeing trees as a weed to be removed, silvopasture integrates them into a sustainable and symbiotic system. Silvopasture is currently practiced on 351 million acres of land globally.  

The dehesa system of silvopasture, famous for the jamón ibérico (Iberian ham) it yields, has been cultivated on the Iberian Peninsula for more than 4,500 years. More recently, silvopasture has taken root in Central America, thanks to the work of champions such as the Center for Research in Sustainable Systems of Agriculture, based in Cali, Colombia. In many places in the US and Canada, livestock and trees can be found intermingling. 

That intermingling takes a variety of forms. Trees may be clustered, evenly spaced, or used as living fencing. Animals may graze in grassy alleys between rows of arboreal growth. Most silvopastoral systems are similar in spacing to a savanna ecosystem. They can be created by planting trees in open pasture, letting those that sprout mature, or by thinning a woodland or plantation canopy to allow for forage growth. 

Soil is the other essential component—and key to the potential silvopasture has for mitigating climate change. Silvopastoral systems sequester carbon in both the biomass above ground and the soil below. Pastures that are strewn or crisscrossed with trees sequester five to ten times as much carbon as those of the same size that are treeless.

Moreover, because the livestock yield on a silvopasture plot is higher, it may curtail the need for additional pasture space and thus help avoid deforestation and subsequent carbon emissions. 

Some studies show that ruminants can better digest silvopastoral forage, emitting lower amounts of methane in the process.
From a financial and risk perspective, silvopasture is useful for its diversification. Livestock, trees, and any additional forestry products, such as nuts, fruit, mushrooms, and maple syrup, all come of age and generate income on different time horizons. Because the land is diversely productive, farmers are better insulated from financial risk due to weather events. 

Silvopasture can also cut farmers’ costs by reducing the need for feed, fertilizer, and herbicides. Because the integration of trees into grazing lands enhances soil fertility and moisture, farmers find themselves with healthier, more productive land over time. 

Work to be done: Though the advantages of silvopasture are clear, its growth has been limited by both practical and cultural factors. These systems are more expensive to establish, requiring higher up-front costs in addition to the necessary technical expertise. There is less incentive to plant trees and protect them where pastures are plentiful, fire poses a risk, or land ownership is unclear. 

Layered on these challenges is the stubborn belief that trees and pasture are not compatible—that trees inhibit the growth of pasture fodder rather than enrich it. Farmers may ridicule one another for shifting to an alternate approach. 

These social impediments make peer-to-peer engagement and direct experience of silvopasture’s benefits key accelerants. To address economic obstacles, international organizations such as the World Bank and NGOs such as the Nature Conservancy are making loans to enable silvopasture installation—loans a typical bank would not provide. 

As the impacts of global warming progress, silvopasture can help farmers and their livestock adapt to erratic weather. Trees create cooler microclimates and more protective environments, and can moderate water availability. Therein lies the climatic win-win of silvopasture. 

Green America resources: Green America’s Re(Store) It! and Carbon Farming programs are accelerating the shift to regenerative agriculture, including silvopasture practices.


Project Drawdown estimates adoption of silvopasture expanding to 554 million acres by 2050 out of 2.7 billion theoretically suitable:

GHG reduction (Plausible Scenario): 31.19 GT of reduced CO2-e by 2050.

GHG reduction (Drawdown Scenario—requires higher rate of adoption): 47.5 GT of reduced CO2-e by 2050..

Cost (Plausible Scenario): $41.6 billion net cost.

Savings (Plausible Scenario): $699.4 billion net savings.

10. Rooftop Solar

rooftop solar (credit drawdown)2.jpg

An Uros mother and her two daughters live on one of the 42 floating islands that the Uru constructed from totora reeds on Lake Titicaca. This solar panel replaced  kerosene and provided electricity to the family for the first time. Photo courtesy of Drawdown.

The problem: The era of fossil fuels is over, and the only question is when the new era of clean energy will be upon us. Solar photovoltaics are only two percent of the global electricity mix at present. 

Solutions in progress: Solar photovoltaics (PV) have seen exponential growth over the past decade. In 2015, distributed systems of less than 100 kilowatts accounted for roughly 30 percent of solar PV capacity installed worldwide. 

While the production of PV panels, like any manufacturing process, involves emissions, they generate electricity without emitting greenhouse gases or air pollution. When placed on a grid-connected roof, they produce energy at the site of consumption, avoiding the inevitable losses of grid transmission. They can help utilities meet broader demand by feeding unused electricity into the grid, especially in summer. This “net metering” arrangement can make solar panels financially feasible for homeowners, offsetting the electricity consumers buy at night, when the sun is not shining.

Rooftop PV is accelerating access to affordable, clean electricity and thereby becoming a powerful tool for eliminating poverty. It is also creating jobs and energizing local economies. In Bangladesh alone, 3.6 million home solar systems have generated 115,000 direct jobs and 50,000 more downstream. 

Roof modules are spreading around the world because of their affordability. Solar PV has benefited from a virtuous cycle of falling costs, driven by incentives to accelerate its development and implementation, economies of scale in manufacturing, advances in panel technology, and innovative approaches for end-user financing.

Small-scale PV already generates electricity more cheaply than it can be brought from the grid in some parts of the US, in many small island states, and in countries including Australia, Denmark, Germany, Italy, and Spain. 
Work to be done: See #8 “Solar Farms.”

Green America resources: Join with your neighbors to drive down the costs of rooftop solar. Read our “Community Solar for All” issue of the Green American.


Project Drawdown estimates that rooftop solar PV can grow from .4 percent of electricity generation globally to 7 percent by 2050.

Carbon reduction (Plausible Scenario): 24.6 GT of reduced CO2 by 2050.

Carbon reduction (Drawdown Scenario—requires more solar rooftops): 43.10 GT of reduced CO2 by 2050.

Cost (Plausible Scenario): $453.1 billion net cost.

Savings (Plausible Scenario): $3.46 trillion net savings.

How Green America Campaigns Stack Up

We thought it would be fun to see where Green America’s climate-related campaigns stack up on the Project Drawdown
top 100 climate-change solutions. The solutions are ranked by the amount of greenhouse gases they reduce by 2050. Here’s how our efforts came out:

Climate Action: Growing Renewables: A big part of our Climate Action program aims to grow renewable energy generation in the US. In 2002, our Solar Catalyst project mapped out the future of solar power in the US. Today, Climate Action supports tax incentives for solar and wind, and helps investors move their money into companies coming up with climate solutions. We also developed the idea for Clean Energy Victory Bonds, which would allow individuals to invest in green energy for as little as $25, through a government Treasury bond. Ranking: Rooftop solar: #10, with 24.6 gigatons (GT) CO2-equivalent (CO2-e) reduced. Solar Farms: #8, with 36.9 GT reduced. Wind Turbines: #2, with 84.6 GT reduced.

Re(Store) It! and Carbon Farming: These campaigns aim to promote regenerative agriculture—through encouraging farmers to practice it, retailers to sell products farmed in this manner, and consumers to look for products grown through regenerative methods. Ranking: Regenerative Agriculture is #11, with 23.14 GT of CO2-e reduced.

Better Paper Project: Our Better Paper Project aims to conserve the world’s forests by advocating for recycled paper
use. Currently, we’re working with magazine publishers to switch them from virgin-pulp paper to paper with at least
some recycled content—particularly Smithsonian Magazine and college and university alumni magazines. The Project’s new “Skip the Slip” campaign asks retailers to offer digital receipts and consumers to skip paper receipts. Ranking: Recycling is #70, with 0.90 gigatons of CO2-equivalent reduced. Saving tropical forests ranks #5 (see p. 23), and saving temperate forests ranks #12, with 22.61 GT of CO2-e.

Fair Trade: Our Fair Trade program empowers women and girls by increasing family income, allowing girls to go to
school (see #6).

Green Living: Our website and publications are filled with practical articles on many of the Project Drawdown solutions, including the ones corresponding to our program areas mentioned above, as well as ride-sharing (#75), investing in
women (#62), composting (#60), saving water (#46), buying an electric car (#26), eating less meat (#4), reducing food waste (#3), and more.

In addition, our “Climate Justice for All” issue of the Green American highlights leaders around the world who are working to reduce climate-change impacts to communities of color, who are often hardest hit by them.

The solutions to climate change are within our abilities, and they improve life for every being on this planet.


From Green American Magazine Issue