Author: Kevin Kircher

Last month, the International Energy Agency¹ (IEA) reported on what the world must do to maintain a livable climate and ensure that all people gain access to modern forms of energy such as electricity and clean cooking². The IEA projects that the United States and other rich nations must reduce greenhouse gas emissions 80% from 2022 levels by 2035. Eighty percent in 13 years. The United States reduced emissions just 7% over the 13 years from 2009 to 2022.

Reducing emissions 80% by 2035 will not be easy, but we do have a clear strategy based on proven technologies that are economically viable today. The strategy consists of two steps, which we can implement concurrently: (1) clean up the power grid, and (2) electrify everything we can.

The animation above shows the Environmental Protection Agency’s latest estimates of United States greenhouse gas emissions. As of 2021, about 29% of United States emissions came from transportation, 25% from electricity generation, 23% from industry, 13% from residential and commercial buildings, and 10% from agriculture and other land use.

If we flipped a magic switch that converted all electricity generation to zero-emission sources, we’d reduce United States emissions by 25%.

If we flipped another switch that replaced all fossil-fueled light-duty vehicles (cars, minivans, pickups, and sport utility vehicles) with electric vehicles, we’d reduce emissions by another 16%³. If we also electrified all fossil-fueled space and water heat in our homes and businesses⁴, as well as all heat for low- and medium-temperature industrial processes⁵, we’d reduce emissions by another 20%, bringing the total reduction to 61%.

We can make these changes using existing technologies that are economically viable today: mainly wind turbines, solar panels, electric vehicles, and electric heat pumps. Other low-emission electricity sources, such as hydropower, geothermal, and nuclear fission, can play significant roles. Electricity and heat storage, as well as flexible energy demand, can promote reliability of energy supply. New power lines can carry renewable electricity from windy and sunny areas to cities.

While these transitions are feasible, they require speed and scale on par with the fastest infrastructure transitions that the United States has ever seen, such as rural electrification in the 1930s and ’40s, the Arsenal of Democracy manufacturing push in World War II, and building the interstate highway system.

It’s long past time to deploy proven technologies as fast as we possibly can. We don’t have time to wait and see if research and development efforts can make unproven technologies — like nuclear fusion or gigaton-scale carbon capture — technically feasible and economically viable. These technologies might help someday, but to echo Jigar Shah, director of the Department of Energy’s Loan Programs Office, now is the time to deploy, deploy, deploy.

What does “deploy, deploy, deploy” look like for individual Americans? It’s pretty simple, really. The next time we need to replace a car or truck, we can get an electric vehicle (or — way more fun! — an electric bike). The next time a furnace, boiler, or air conditioner needs replacement, we can get an electric heat pump. The next time a water heater or stove needs replacement, we can get a heat-pump water heater or induction stove. (The nonprofit Rewiring America publishes guides to planning home electrification projects and accessing rebates and tax breaks.) We can also install rooftop solar panels, join community solar programs, or sign up for a clean electricity plan if our utility offers one.

In addition to individual action, we need systemic change to accelerate clean-up of the power grid and electrification. We can vote, particularly in primaries and close general elections, for candidates who promise climate action. (Organizations like Climate Cabinet support candidates for state office who prioritize climate action.) Once candidates get elected, we can push them to deliver on their promises of climate action. We can do this alone, through office visits, phone calls, letters, social media, or email. Better yet, we can join groups that organize collective action. We can also divest our savings, if any, from banks that fund fossil fuel companies. (Marilyn Waite, the managing director of the Climate Finance Fund, maintains a list of sustainable banking and investment options.)

The parallel two-step strategy of cleaning up the power grid and electrifying everything we can will not, on its own, deliver all of the emission cuts that we need. But this strategy will go a long way toward deep decarbonization — 61% is not so far from 80% — and we can implement it using existing technologies that are economically viable today. To borrow a phrase from the IEA report, “the fierce urgency of now” requires it.

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1. Per Wikipedia, the IEA is an intergovernmental organization with 31 member countries and 13 associate countries, who collectively use 75% of global energy. ↩︎
2. From Chapter 2 of the IEA report, about 35% of the world’s eight billion people currently lack access to electricity, clean cooking, or both. ↩︎
3. The EPA estimates that 58% of transportation-sector emissions come from passenger-cars (21%) and light-duty trucks (37%), which include minivans, pickups, and SUVs. ↩︎
4. The US Energy Information Administration estimates that 93% of fossil fuels burned in residential buildings go to heat space or water. Similarly, the IEA estimates (see Tables C1, E8, and E10) that space and water heat comprise 79% of fossil fuel burning in commercial buildings. Combining the residential and commercial numbers based on fossil fuel use in each sector, space and water heat comprise an estimated 89% of fossil fuel use in buildings. ↩︎
5. A recent report on industrial electrification estimates that 13% of fossil fuel use in industry is in conventional boilers and another 21% is for process heat below 300 °C. ↩︎

I intend this guide for grad students in my engineering research group. Some of the recommendations apply broadly, but others are specific to me or my field.

Why should I publish research papers?

Most researchers hope their work improves the real world in some tangible way. Publishing doesn’t guarantee that, but it helps.

Publishing also helps professors get tenure, raises, and promotions; and helps students get jobs in academia and research labs.

How many papers should I publish?

For most purposes, the more the better.

In my field, professors typically expect one good first-author journal paper for a master’s degree and three for a PhD. Conference papers and non-first-author journal papers usually don’t count.

Who decides whether my paper gets published?

Editors and peer reviewers.

A submitted journal paper goes to an editor, who screens it for perceived quality and relevance to the journal’s scope. If the paper passes that check, the editor sends it to one or more peer reviewers. Reviewers read the paper, or at least skim it, and score its originality, correctness, and impact. Reviewers submit scores to the editor, who decides whether to reject the paper, accept it conditioned on revisions, or accept it as is.

Most conferences work similarly.

What makes a paper publishable?

Publishable papers are papers that editors and reviewers believe are original, correct, and impactful.

Some people think that doing a lot of work entitles them to publication. Others think that papers that are easy to write must be unpublishable. Neither view is accurate.

How do I show originality?

Original papers create new ideas, theorems, methods, algorithms, data, statistics, software, or physical objects. To convince editors and reviewers of originality, authors should (a) show that they understand related work, and (b) state several creations in their paper that don’t exist in related work. Each of those creations is a contribution.

When trying to show originality, authors sometimes dismiss or deride related papers. I don’t recommend this. The authors of those papers may be your reviewers. Also, it’s rude.

How do I show correctness?

In theory, a paper should demonstrate inarguably that its contributions are correct.

In practice, editors and reviewers rarely have time to check this. Instead, they check things they view as proxies for correctness. Authors can improve their odds of passing correctness checks by using good grammar, spelling, and logic; showing that they understand related work; clearly explaining all methods; using standard, consistent mathematical notation; defining all symbols; making figures easy to understand; and sharing all data and code necessary to validate their contributions.

How do I show impact?

Explain how the contributions could tangibly improve the real world.

Which individuals, businesses, or government bodies could use the contributions? How could the contributions change behavior, products, or policies? What improvements to the real world could those changes cause? How large could those improvements be? Who could benefit?

For example, suppose you create a control algorithm that improves air conditioner efficiency by 15%. Manufacturers could add your control algorithm to their air conditioners. A typical family could save $75 per year on energy bills. Communities near power plants could breathe less air pollution and suffer less respiratory illness. The world could emit 1% less greenhouse gas pollution, slow climate change slightly, and inflict less suffering on disadvantaged people.

Where should I focus my efforts?

The title, abstract, figures, and statement of contributions.

Few people who interact with your paper will reach the main body of text, as the figure below illustrates. You can increase the number of people who actually read the paper by (a) publishing in a good journal, which increases the number of potential readers; and (b) shaping the title, abstract, and figures to draw in potential readers.

Better journals get more readers. Readers are busy and the world is full of bad papers. Good journals save readers time by filtering out bad papers. Publishing in a good journal requires a convincing statement of contributions; see “How do I show originality?”

My favorite kind of title states the paper’s best contribution in a simple sentence. My least favorite titles use acronyms and jargon. Some good titles ask provocative questions, which the abstracts answer.

A good abstract gives away the whole paper. It tells readers why they should care about the topic, what past work has shown, what contributions the paper makes, and how the contributions could tangibly improve the real world.

Figures should make sense to people who’ve only read the title and abstract. Legends and axis labels should use words, not acronyms or symbols. Text in figures should be about as big as text in the body. Each figure should convey one key message. Any element of a figure that doesn’t help convey the figure’s key message should be cut. Most figures should showcase the paper’s contributions — typically with one or two figures or tables per contribution — but a couple of figures can illustrate the problem or methods.

As I write the body of a paper, I periodically stop and read it out loud. Can I audibly say the words I wrote without confusing myself, cringing at the sound of my own voice, or boring myself to sleep? I find this almost a necessary and sufficient condition for decent writing.

A few style tips:

• Shorten words, sentences, paragraphs, papers. To respect busy readers, get to the point.
• Use mostly active voice (“Fig. 3 shows…”), not passive (“It can be seen from Fig. 3 that…”).
• Kill your adjectives.
• Restrict each paragraph to one main idea, encapsulated in its first sentence.
• Use few or no acronyms. Readers jump around papers; an acronym defined on page three may alienate a reader who jumps from page one to six.
• Spell out the integers zero through nine and any number that starts a sentence. Write all other numbers as numerals (12, -3, 2.718, etc.).

Using energy in homes causes 16% of United States greenhouse gas emissions¹ and costs Americans $230 billion each year. About half of those emissions and costs come from heating and cooling homes.

We can reduce emissions and costs from heating and cooling in several familiar ways. We can keep our homes cooler in winter and warmer in summer. We can choose milder thermostat settings when we go to bed or leave home². Homeowners can invest in insulation, air sealing, good windows, and efficient heating and cooling equipment. Governments can pass codes that make landlords to do the same.

But there’s another, less familiar way to reduce demand for heat and cooling: Living in dense housing.

Homes in dense buildings (such as apartments, row houses, and condos) share walls with adjacent units, so have less wall area facing the outdoors. That means less heat lost to the outdoors and less heat needed from the furnace, boiler, or heat pump.

This “save energy by sharing surfaces” effect is why my cats used to get so snuggly on cold days. They lost no heat through whatever parts of their bodies they could get into contact with each other. Similarly, an apartment loses little heat through walls it shares with other units.

Sharing walls can save surprising amounts of energy. As the figure below shows, a stand-alone house has twice as much exterior wall area as a unit with the same floor area in a four-unit multi-family building. That means the multi-family unit needs about half the heat in winter and half the cooling in summer. Half the demand, half the emissions, half the costs.

Data from the Energy Information Administration’s Residential Energy Consumption Survey support this theory. On average over the United States, detached single-family houses use about 19 thousand BTU per square foot per year for space heating³. Apartments in buildings with five or more units use about 10 thousand BTU per square foot per year⁴. Half the demand, half the emissions, half the costs.

Cutting a house’s heat demand in half through renovations – such as insulating, air-sealing, and replacing windows and heating equipment – is very difficult. While energy-efficiency renovations of that depth are possible, they often take years and cost tens of thousands of dollars.

Dense homes can have other benefits. They tend to be in dense neighborhoods, where people can get to friends, food, and fun without driving. Driving less reduces emissions, fuel costs, traffic, and the number of people that car crashes injure or kill. Dense homes also tend to use space more effectively than stand-alone houses, letting residents live comfortably in less space. This can further reduce demand for heat and cooling.

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1. According to the EIA, residential and commercial buildings caused 29% of US greenhouse gas emissions in 2022, including indirect emissions due to electricity use. Buildings also used 40% of final energy (22% residential, 18% commercial). Allocating emissions between the residential and commercial sectors in proportion to their energy use gives a residential emissions estimate of 0.29*0.22/0.4 = 0.16, or 16%. ↩︎
2. Shameless plug: My research group works on ways to automate thermostat adjustments to reduce demand for heat and cooling, improve equipment efficiency, and keep occupants comfortable. ↩︎
3. The average US single-family home has 2,264 square feet of floor area and uses 44.0 million BTU per year for space heating. ↩︎
4. The average US apartment in a building with five or more units has 905 square feet of floor area and uses 9.1 million BTU per year for space heating. ↩︎

Purdue’s campus occupies traditional homelands of the Bodéwadmik (Potawatomi), Lenape (Delaware), Myaamia (Miami), and Shawnee peoples, who are the original Indigenous caretakers of the land.

White settlers forced most Indigenous people out of Indiana after the federal government passed the Indian Removal Act of 1830. In 1838, for example, Indiana’s governor ordered a militia to burn a Potawatomi village, home to 859 people, and march them at gunpoint to a reservation in Kansas. In this forced removal, called the Potawatomi Trail of Death, militia members killed 28 children and 14 adults.

Purdue is also a land-grant university. In 1865, the federal government gave the state of Indiana 380,000 acres of land, spread across states ranging from Michigan to Montana. The U.S. had taken that land from Indigenous people by treaty, coercion, or violence. Per the Morrill Land-Grant Act of 1862, this gift of Indigenous land came with the obligation to establish a university teaching agriculture, the mechanical arts, and military tactics.

The state of Indiana sold the gifted Indigenous land and used the proceeds to endow Purdue with $340,000 in 1874. Adjusted for inflation and assuming investment at a 4% annual rate of return, $340,000 in 1874 translates to about $3 billion in 2023. Purdue’s total endowment is currently $3.7 billion.

This High Country News article and the associated data repository have more information on the history of land-grant universities and Indigenous peoples.

Purdue’s Native American Educational and Cultural Center supports students from Indigenous backgrounds, who currently make up about 0.2% of the student body.

Wind and solar power are now among the least-cost options for new electricity generation. The following figure, from Lazard’s 2023 report,  shows the current unsubsidized levelized cost of energy (LCOE) for various sources in the United States. LCOE is the ratio of all lifetime (discounted) costs to lifetime energy production. The unsubsidized LCOEs of utility-scale solar and onshore wind (circled) are now at or below the LCOEs of all conventional power plants (bottom four rows), including natural gas combined cycle.

Since 2009, wind and solar costs have declined by about 66% and 84%, respectively. The following plots, also from Lazard’s 2023 report, show the unsubsidized LCOEs of onshore wind (top) and utility-scale solar (bottom) in the United States from 2009 to 2023.

These cost declines are incredible success stories of research, development and deployment. They have made clean, renewable power the least-cost option in many settings. This new alignment of incentives between cutting emissions and making money has made wind and solar power two of the largest sources of new electricity generation capacity in the United States, as this Canary Media chart of 2023 capacity additions shows.

The Intergovernmental Panel on Climate Change (IPCC), a United Nations group that synthesizes climate science, issued its latest report in August, 2021. This report reiterates what we’ve known for many decades: human activities, especially burning fossil fuels, are heating the planet. But the report also summarizes recent advances in attribution science, which show how human-caused heating is increasing the frequency and severity of heat waves, droughts, floods, storms, hurricanes, and wildfires.

These natural disasters are causing real harm to people. In the United States, for example, the National Oceanic and Atmospheric Administration has tracked natural disasters since 1980. The following graph, from their 2021 Billion-Dollar Weather and Climate Disasters report, shows the numbers and costs of natural disasters in the United States that caused more than $1 billion in damages (inflation-adjusted to 2021 dollars). The bars in this graph are the numbers of billion-dollar disasters each year. The curves show the annual costs of these disasters (brown, with the 95% confidence intervals shaded in gray) and the five-year moving average of these costs (black).

The striking message of this graph is that natural disasters in the United States are becoming more frequent and severe. In the last five years, these disasters have cost about $640 billion and killed about 4,000 people. While not all of these natural disasters can be attributed to climate change, we now know that human-caused heating is increasing their frequency and severity.

If we don’t act quickly to cut greenhouse gas emissions, we will likely see more, worse natural disasters in the coming decades. According to the IPCC’s report on climate impacts, we should also expect to see more poverty, reduced crop yields, more water scarcity, higher rates of food- and water-borne diseases, and rising seas submerging coastal communities. These factors are likely to drive millions of people from their homes and increase risks of violent conflict. The impacts will disproportionately harm vulnerable people, in both developing and developed countries.

For me, climate action is fundamentally about reducing human suffering: poverty, hunger, thirst, disease, displacement, injury, and death. To reduce that suffering, we can and must slow climate change and prepare for those impacts of climate change that we can no longer avoid.