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Errata & Updates

Drawdown is a living book. Key errata and updates, since first printing in 2017, are listed here.

Language, p. xii

Revised Caption: The decree carved into the Rosetta Stone in Egypt in 196 B.C. is known less for its content—an affirmation of the rule of King Ptolemy V—than for its unique combination of scripts. The same text repeats in Greek, Egyptian hieroglyphics, and Egyptian demotic, respectively royal, sacred, and common languages of the time. In the 19th century, European scholars used the Rosetta Stone to crack the code of hieroglyphics, opening up understanding of Ancient Egypt. Today, the Rosetta Stone is what Richard Parkinson, professor of Egyptology at Oxford, calls “an icon of…decipherment” and “a symbol of our desire to understand each other.” To convey and comprehend through language is at the heart of the human endeavor.

Numbers, p. xiv

Other heat-trapping gases that we measure include methane, nitrous oxide, and fluorinated gases.

The degree to which a given solution has a bearing on greenhouse gases is translated into gigatons of carbon dioxide removed between 2020 and 2050. You will see that number presented as “reduced CO2” for each solution.

Thirty-six gigatons is the amount of carbon dioxide emitted in 2016.

We also provide additional information about our research, sources, and assumptions at

Wind, p. 2

Today, 314,000 wind turbines supply 3.7 percent of global electricity.

Correction (Offshore): $545.3 BILLION NET COST  $762.5 BILLION NET SAVINGS

Caption: The wind farm consists of 88 Siemens 3.6-megawatt turbines placed over a 14-square-mile area, 11 miles from shore.

In Germany in 2015, bottlenecks in the grid caused 4,100 gigawatt-hours of wind electricity to be wasted—enough energy to power 1.2 million homes for a year.

An increase in onshore wind from 3 to 4 percent of world electricity use to 21.6 percent by 2050 could reduce emissions by 84.6 gigatons of carbon dioxide.

At a combined cost of $1.8 trillion, wind turbines can deliver net savings of $8.2 trillion over three decades of operation.

Solar Farms, p. 9

Deletion: [...] which tends to pick up at night.

Biomass, p. 16

Perennial herbaceous grasses such as switchgrass and Miscanthus can be harvested for fifteen years before replanting becomes necessary […].

Germany currently produces 7 percent of its energy from biomass.

Nuclear, p. 19

There are more than 440 operating nuclear reactors in 30 countries, and 60 more are under construction. Of the 30 countries with operative nuclear power plants, France has the highest nuclear contribution to its electrical energy supply, at over 70 percent.

China has thirty-seven nuclear plants operative and twenty under construction.

Romm summarizes the perspective of the International Energy Agency (IEA): nuclear can play “an important but limited role.”

China [...] is committing to a combined wind and solar capacity of 320 gigawatts by 2020.

Methane Digesters, p. 26

Molecules of methane […] create a warming effect up to thirty-four times stronger than carbon dioxide over a one-hundred-year time horizon.

The cumulative result: 10.3 gigatons of carbon dioxide emissions avoided at a cost of $217 billion.

In-Stream Hydro, p. 27

If in-stream hydro grows to supply 3.7 percent of the world’s electricity by 2050, it can reduce 4 gigatons of carbon dioxide emissions and save $568.4 billion in energy costs.

Waste-to-Energy, p. 28

Today, the United States burns more than 30 million tons of garbage annually—roughly 13 percent of its total generated waste.

In Europe, more than 480 waste-to-energy plants exist, burning roughly a quarter of all waste. Sweden is among the leaders.

In Europe [...] a 50 percent recycling directive is in place for the year 2020.

Energy Storage (Utilities), p. 33

All told, there are more than two hundred pumped storage systems in the world at present, accounting for 99 percent of global storage capacity.

Farmland Restoration, p. 41

Lal estimates that farmland soils could reabsorb 88 billion to 110 billion tons of carbon.

Food Waste, p. 42

Ranked with countries, food waste would be the third-largest emitter of greenhouse gases globally […].

Multistrata Agroforestry, p. 46

[…] rates of carbon sequestration that are comparable to those of afforestation and forest restoration—2.8 tons per acre per year, on average.

One study suggests every acre of agroforestry can prevent deforestation of five to twenty forest acres.

Multistrata agroforestry requires a humid climate and cannot be implemented everywhere […]. 

According to one study of traditional Pacific multistrata agroforestry, just 0.02 calories of energy produce 1 calorie of food.

Improved Rice Cultivation, p. 48

[…] its global warming potential is up to thirty-four times greater.

Silvopasture, p. 50

It is one approach within the broader umbrella of agroforestry and revives an ancient practice, now common on over 350 million acres worldwide.

Experts around the world are engaged in an ongoing and fiery debate about how best to manage pastures to counterbalance the methane emissions of livestock […].

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, depending on specifics of analysis.

Farmers could realize financial gains from revenue diversification of $699 billion, for a total net cost of $42 billion to implement.

Regenerative Agriculture, p. 55

They include no tillage, diverse cover crops, on-farm fertility (no external nutrient sources required), no or minimal pesticides or synthetic fertilizers, and multiple crop rotations […].

Farms are seeing organic matter levels rise from a baseline of 1 to 2 percent up to 5 to 8 percent over ten or more years.

Nutrient Management, p. 57

The United Nations Environment Programme estimates that a 20 percent improvement in nutrient use would eliminate more than 20 million tons of nitrogen fertilizer and produce potential savings of $50 billion to $400 billion.

Tree Intercropping, p. 59

Evergreen agriculture, another variation of tree intercropping, calls for a discontinuous cover of scattered trees […].

Yields can increase by a factor of three, without chemical fertilizers or other inputs.

Conservation Agriculture, p. 61

Conservation agriculture sequesters a relatively small amount of carbon—an average of half a ton per acre.

Biochar, p. 64

Revision: It was the hallmark of an agricultural system that differs dramatically from pervasive practices today: the wholesale conversion of Amazonian forest to annual crops, such as soybeans for livestock feed. When forest is cleared and vegetation burned, a residual layer of carbon remains, but only for a short period of time.

Image & Caption: 12–61   61–202   Tons per acre to a depth of one yard.

Tropical Staple Trees, p. 66

Today, 89 percent of cultivated land, about 3 billion acres, is devoted to annuals. Of the remaining land in perennial crops, 116 million acres are used for perennial staple crops.

Or enset, a banana-like plant in Ethiopia that is fermented […] to make a traditional staple dish called kocho.

Perennial staple tree crops can thrive under conditions that annuals cannot.

For example, an enset can go dormant for six to eight years […]; when rain returns, the enset returns as well.

Farmland Irrigation, p. 68

Deletion: And some crops, such as rice, are simply not suited to drip or sprinkler irrigation.

Managed Grazing, p. 72

[…] the world is beset with more than a billion acres of land in this condition, according to some estimates.

Improved grazing typically sequesters a few hundred pounds of carbon per acre, but in some cases as much as three tons per acre.

Many who started at 1 percent organic matter are now at 6 to 8 percent, or more.

Brown has taken soil organic matter from 4 percent to 10 percent in six years.

Family Planning, p. 79

Two hundred and fourteen million women in lower-income countries.

The resulting emissions reductions could be 119.2 gigatons of carbon dioxide.

Educating Girls, p. 82

Today, 130 million girls are denied the right to attend school.

Walkable Cities, p. 87

Walkways are well lit at night, tree-lined and shaded during the day (vital in hot, humid climates).

Heat Pumps, p. 95

The thermometer recorded the temperature, which dropped to seven degrees Fahrenheit […].

Smart Glass, p. 97

Correction: $932.3 BILLION NET COST

Smart Thermostats, p. 98

Originating in North America and migrating to Europe, smart thermostats occupy a fraction of the addressable market at present.

Correction: $74.2 BILLION NET COST

Landfill Methane, p. 100

Over the course of a century, it has up to thirty-four times the greenhouse effect of carbon dioxide.

Retrofitting, p. 103

The Empire State Building will save $4.4 million in energy costs and avert more than 100,000 tons of greenhouse gas emissions.

Forest Protection, p. 109

Primary forests contain 300 billion tons of carbon […].

These strategies include […] market-driven mechanisms, primarily eco-certification programs that inform consumers and affect purchasing decisions (many corporations have signed deforestation commitments); truly sustainable timber and agricultural practices […].

The most prominent pay-for-performance program is the United Nations Reducing Emissions from Deforestation and Forest Degradation (REDD+) program, which began to take shape in 2005. Funding programs are emerging out of the 2014 New York Declaration on Forests, endorsed by forty countries and nearly sixty multinational corporations, among others. The Forest Carbon Partnership Facility, a multi-sector effort meant to assist REDD+ efforts, has established two funds of nearly $1.1 billion total […].

Achim Steiner, former executive director of the United Nations Environment Programme […].

It is difficult to estimate what it would “cost” to save it all. One study asserts that for $50 billion per year—about 3 percent of the world’s military spending—tropical deforestation could be reduced by two-thirds.

[…] forest protection and tropical and temperate forest restoration together are one of the most powerful solutions available to address global warming.

Coastal Wetlands, p. 112

According to the journal Nature, the soil of mangrove forests alone may hold the equivalent of more than two years of global emissions […].

Tropical Forests, p. 114

“More than 2 billion hectares [4.9 billion acres] worldwide offer opportunities for restoration—an area larger than South America,” a team of WRI researchers reports.

Restoring 865 million acres of forest between now and 2030 could cost $350 billion and as much as $1 trillion.

“Achieving the 350 million-hectare [865 million-acre] goal could generate $170 billion per year in net benefts from watershed protection, improved crop yields, and forest products […].”

Deletion: Only carbon stored in soil organic matter and aboveground biomass is accounted for; below-ground biomass is not included.

Perennial Biomass, p. 121

Perennial biomass crops provide the feedstock for biomass energy generation, making those emissions reductions possible.

Peatlands, p. 122

Ranging in depth from two feet to more than sixty, layers of peat contain enormous amounts of carbon.

Afforestation, p. 134

In an area the size of six parking spaces, a three-hundred-tree forest can come to life—for as little as the cost of an iPhone.

High-speed Rail, p. 138

In 1964, Japan celebrated the Olympics by inaugurating the world’s first high-speed “bullet” train on the Osaka–Tokyo route, a distance of 320 miles.

China has by far the most high-speed rail lines—more than 50 percent of the total— followed by Western Europe and Japan.

Compared to driving or flying, it is the fastest way to travel between two points a few hundred miles apart […].

Cost estimates have doubled from $33 billion to $68 billion.

The tracks typically range from $15 million to $80 million per mile; and then there are bridges, tunnels, and viaducts. In the Northeast Corridor, Amtrak estimates that creating a high-speed rail system rated at 220 miles per hour would cost roughly $150 billion.

High-speed rail requires many passenger trips to break even.

The carbon footprint of an up-and-running HSR is lower than that of planes and cars, but only when it replaces significant air and vehicle trips.

Correction: $1.05 TRILLION NET COST

Ships, p. 140

More than 80 percent of global trade, by weight, floats its way from place to place.

Key efforts aim to improve ship design and the technology onboard.

Considering that trillions of dollars of goods are shipped annually, it may fall to the companies whose goods are being transported to pressure maritime shipping into being a responsible industry.

Electric Vehicles, p. 143

China has more than 170,000 electric buses.

They can charge the car off-peak, when electricity is cheapest […].

If EV usage rises to 16 percent of total passenger miles by 2050, 10.8 gigatons of carbon dioxide from fuel combustion could be avoided.

Ridesharing, p. 145

For every one hundred cars being driven to work in the United States today, only five carry another commuter.

Electric Bikes, p. 147

In 2014, e-bike riders traveled 360 billion miles, largely in China.

Cars, p. 149

Those additional 315 million cars can reduce carbon dioxide emissions by 4 gigatons by 2050, saving owners $1.76 trillion in fuel and operating costs over three decades.

Revised Caption: In 2007, General Motors introduced the Chevrolet Volt Concept Car, a plug-in electric hybrid, at the North American International Auto Show. According to GM estimates upon debut, the car’s battery-powered electric motor sustains it solo for up to 40 miles, after which the combustion engine kicks in to create electricity, replenish the battery, and extend range to 640 miles. If charged overnight and driven 60 miles daily, fuel efficiency is an astonishing 150 miles per gallon.

Planes, p. 150

The pollutants that trail movement by flight—carbon dioxide, nitrogen oxides, water vapor in contrails, black carbon—are not.

Those gains were largely thanks to fleet upgrades, while airlines also sought to maximize the number of passengers on each plane.

Trucks, p. 153

Diesel trucks were first introduced in the 1930s, hit their stride in the 1950s, and now move roughly half of land freight.

There are two main tracks for reducing the ratio of fuel used per ton of freight moved […].

Based on 2010 U.S. prices, investing in a typical package of modernizations for a new truck can cost around $30,000 […].

Payback periods for some technologies are short—as little as one to two years.

Trains, p. 156

Revised Caption: A General Electric Evolution Series Tier 4 locomotive before being painted at its factory in Fort Worth, Texas. This family of diesel-electric locomotives is among the most efficient in the world with respect to emissions, achieving a 70 percent reduction in particulate matter and nitrous oxide compared to Tier 3 predecessors. (Tier 4 is the U.S. Environmental Protection Agency standard for new locomotives, effective since January 1, 2015.) This 440,000-pound behemoth can move one ton of freight 500 miles on one gallon of fuel. Sensors throughout the engine gather real-time data to diagnose and improve performance and efficiency. Many Tier 4 locomotives can be found hauling freight along the rail corridor that runs between Los Angeles and Seattle.

If that increases to 621,000 miles by 2050, emissions from fuel use for freight operations alone can be reduced by 0.5 gigatons of carbon dioxide.

Household Recycling, p. 159

Also on the rise are stronger targets for municipal recycling rates, such as the European Union’s proposed 65 percent by 2030.

Refrigeration, p. 164

Their replacement chemicals, primarily hydrofluorocarbons (HFCs), have minimal deleterious effect on the ozone layer […].

HFC substitutes are already on the market, including natural refrigerants such as propane and ammonia. Carbon dioxide itself can be used in specially designed systems that achieve much higher pressure.

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

Caption: HFCs are largely innocuous to the ozone layer, but they are one of the most potent greenhouse gases known to humankind.

Revision: Our analysis includes emissions reductions that can be achieved through the management and destruction of refrigerants already in circulation. Over thirty years, containing 87 percent of refrigerants likely to be released could avoid emissions equivalent to 89.7 gigatons of carbon dioxide. Phasing out HFCs per the Kigali accord could avoid additional emissions equivalent to 25 to 78 gigatons of carbon dioxide (not included in the total shown here). The operational costs of refrigerant leak avoidance and destruction are high, resulting in a projected net cost of $903 billion by 2050.

Marine Permaculture, p. 180

Given that Hurricane Katrina alone cost $108 billion and that 2015 saw twenty-two Category 4 or 5 hurricanes, this may be a cost-effective solution.

Intensive Silvopasture, p. 181

Silvopasture is a common form of agroforestry, practiced today on over 350 million acres worldwide.

In a five-year study of intensive silvopasture […] the rate of carbon sequestration was roughly three tons per acre, a high rate for any land use.

Autonomous Vehicles, p. 185

The contemporary car is […] a parking machine for which some 700 million parking spaces have been built in the U.S. alone […].

Given […] the average U.S. ownership cost of $9,000 per year, the pay-as-you-go model for on-demand vehicles will appeal to rich and poor alike.

Solid-state Wave Energy, p. 187

The kinetic force of oceans, which surge with roughly 80,000 terawatt hours of energy annually, is extraordinary. It is a staggering amount of energy—enough to power human needs at least 100 times over.

A single terawatt is the equivalent of 1 trillion watts and sufficient to provide electricity to 33 million U.S. homes each year.

Living Buildings, p. 189

Today, however, there are more than 350 buildings in various stages of certification, encompassing several million square feet in two dozen countries.

Microbial Farming, p. 200

A gram is 0.035 ounce […].

The process creates emissions from fossil fuel energy generation, and much of that nitrogen ends up in the sky as nitrous oxide […].

Industrial Hemp, p. 202

The United States effectively banned the cultivation of all types of hemp in 1937.

Perennial Crops, p. 203

Herbaceous perennials die back too, but not the roots, which produce new growth beneath the soil.

A Cow Walks onto a Beach, p. 205

Most critically, Asparagopsis taxiformis could dramatically reduce livestock methane emissions, which now account for 6 to 7 percent of greenhouse gases released around the world each year.

Ocean Farming, p. 207

Nitrous oxide is the greenhouse gas you do not pay attention to.

An Opening, p. 217

In the electric power generation industry, more people in the U.S. as of 2016 are employed by the solar industry than by gas, coal, and oil combined.

What Do the Numbers Tell Us, p. 220

[…] the net cost to implement all solutions modeled here is $30 trillion over thirty years.

Because the data are dynamic and constantly being up dated to show changes, what you see on our website is not necessarily the same as the numbers you see here. We are working towards producing a dashboard for each solution. At that point, you can modify the major inputs and come to different conclusions about future impacts and costs.


Corrected Total (all 80 solutions) for Plausible Scenario: 1,050.89 GT

Summary of Solutions by Overall Ranking, p. 222

Corrected Table Heading: NET SAVINGS

Corrections within Table:

  • Wind Turbines (Offshore): 14.09 GT
  • Smart Thermostats: $74.16 Net Cost
  • Smart Glass: $932.30 Net Cost
  • High-Speed Rail: $1,049.98 Net Cost
  • Totals: 1,050.89 GT | $29,620.83 Net Cost | $74,305.09 Net Savings
Summary of Solutions by Sector, p. 224

Corrected Table Heading: NET SAVINGS

Corrections within Table:

  • Smart Thermostats: $74.16 Net Cost
  • Smart Glass: $932.30 Net Cost
  • Buildings and Cities Totals: 54.49 GT | $4,926.62 Net Cost
  • Wind Turbines (Offshore): 14.09 GT
  • Energy Totals: 246.13 GT
  • Afforestation: $29.44 Net Cost | $392.33 Net Savings
  • Bamboo: $23.79 Net Cost | $264.80 Net Savings
  • Perennial Biomass: $77.94 Net Cost | $541.89 Net Savings
  • Land Use Totals: $131.17 Net Cost | $1,199.02 Net Savings
  • High-Speed Rail: $1,049.98 Net Cost
  • Transport Totals: 45.68 GT | $17,764.32 Net Cost | $22,608.53 Net Savings
Drawdown Fellows, p. 226

Addition: Jai Kumar Gaurav, MSc is a research analyst with eight years of experience working in the field of climate change mitigation and adaptation. He has worked on Clean Development Mechanism and Gold Standard certified voluntary emission reduction projects. He is also working on developing a Nationally Appropriate Mitigation Action (NAMA) proposal in the waste sector.

Drawdown Advisors, p. 230

Addition: Jonathan Foley spent over two decades leading interdisciplinary, university-based programs focused on solving global environmental issues before becoming the Executive Director of the California Academy of Sciences, where he has been able to incite interest and excitement in the sciences in children and adults alike. He has published over 130 scientific articles, many op-eds, and has won numerous awards and honors, including the Presidential Early Career Award for Scientists and Engineers (awarded by President Bill Clinton).

Addition: Martin Siegert is co-director of the Grantham Institute for Climate Change at Imperial College London, and previously was director of the Bristol Glaciology Center at Bristol University as well as head of the School of GeoSciences at Edinburgh University. An expert in geophysics, he was awarded the Martha T. Muse Prize for excellence in Antarctic science and policy in 2013, and is a fellow of the Royal Society of Edinburgh.

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