As scientist-activists who work on climate science and renewable energy, the question we get asked the most is, “What can I do about climate change?”

Here’s our evolving take – a synthesis of what we think are the three most impactful ways to contribute in the face of such an urgent and systemic problem. (To avoid catastrophic climate change, global greenhouse gas emissions have to start falling , now, faster than they have risen for the past 160 years.)

Our “theories of change” are informed by our understanding of climate science and clean energy, by our journey from scientists to scientist-activists, and, most of all, by the insights of other academics and activists.

Leverage our collective power

Even a homeless person in America has a carbon footprint of roughly 8.5 tons of carbon dioxide per year — far higher than the per capita value needed to hold back dangerous climate change. So no matter how much we try to cut our individual greenhouse gas emissions, it won’t be enough. Not while our energy continues to be supplied almost entirely by fossil fuels.

Yet the infuriating reality is that we already have most of the efficiency and clean energy technologies we need to do away with fossil fuels. The fossil fuel industry , in large part, is standing in the way of their accelerated deployment and cost reduction.

This is hardly surprising when the business model of these companies is fundamentally incompatible with the science of mitigating climate change. And when that model — like our society as a whole — prioritizes economic growth above ecological protection and actual human well-being.

Yes, we are all complicit in climate change. But you and I are passively guilty — stuck in a high-carbon system. Fossil fuel interests and political ideologues, on the other hand, are actively guilty — working to stop the system from changing.

This is where collective action comes in. As 350.org co-founder Bill McKibben argues , the only thing powerful enough to take on the financial might and political power of the fossil fuel industry is the power of a social movement.

This isn’t just rhetoric: historical evidence suggests that it takes roughly 3.5 percent of the population to sustain a winning social movement. The single most important thing we can each do is to be part of the collective 3.5 percent.

“ Ask the Tea Party. Ask the civil rights movement,” says McKibben.

The question I get asked the most: What can I do to make a difference? It's almost the right question https://t.co/e6rdJIj8zg — Bill McKibben (@billmckibben) October 14, 2016

We all belong to one or more constituencies that can either support the status quo, or challenge it. These so-called “ pillars of support ” are our points of leverage. Examples include students pushing their universities to divest from fossil fuel companies, mothers lobbying for statewide access to clean energy, doctors raising public awareness, children suing the government and fossil fuel companies over intergenerational injustice, and frontline communities blocking fossil fuel expansion.

To get started, explore existing campaigns and join one that resonates strongly with your values, passions, and background. Many excellent ones are listed here , here , and here ; if none are for you, consider starting your own.

Look not just to D.C., but also to your local community — it’s there that many of the most consequential battles will happen over the next four years, and it’s there that you can have outsized impact. Take part in sustained organizing, and also make sure you show up to flashpoints of unity and momentum like marches, rallies, and protests. Resistance groups like Indivisible and the Town Hall Project offer resources on how to effectively pressure elected officials.

You may also be able to bring relevant skills and expertise to bear on the climate movement. From filmmakers documenting grassroots campaigns, to lawyers defending activists, to scientists providing expert testimony, to musicians inspiring action, “no matter what interests you pursue or career path you follow,” says Vox’s David Roberts, “you will have some influence. Use it!”

End climate silence

Climate communication experts have found that although most Americans say global warming is important to them, many don’t hear about it in the media or from people they know.

Indeed, 70 percent of Americans “rarely or never discuss global warming with family and friends.” In 2016, despite record high temperatures and the historic Paris Climate Agreement, climate change news coverage on evening newscasts and Sunday shows from ABC, CBS, NBC, and Fox amounted to a meager total of 50 minutes .

The result is a “spiral of silence”: Silence begets silence, making political inaction all too easy.

As climate commentator Joe Romm has urged : “Talk about climate change and its solutions with everyone you know a lot more than you do now.” Be vocal on social media, at local events, and with elected officials, write opinion articles, and, most importantly, talk to friends, families, and coworkers.

What should we talk about? Values. There is overwhelming evidence from behavioural science and marketing that values, not facts, are the currency of persuasion. Don’t just talk about what is happening or needs to happen, talk about why it matters.

Themes like jobs, national security, and public health and safety resonate widely with the American public. Clean energy, for instance, can offer a winning, “all-American” narrative about job creation, health benefits, and energy independence. You don’t need to be a climate expert to talk about why you care. See here for how climate change threatens what we love, here for denial debunking, and here for climate science 101.

How do we tell our stories? Marshall Ganz’s " Self, Us, Now " storytelling framework is a learnable, proven formula we highly recommend. Simon Sinek’s " Why, How, What " is another good blueprint.

Cut the biggest chunks of your carbon footprint

Reducing your largest sources of greenhouse gas emissions is a low-barrier way to contribute. It’ll also save you money.

However, be aware that taking collective action and ending climate silence are more impactful than personal greening, because whereas the latter is linear, the first two are exponential.

The exception is when our individual actions send social signals to those around us, creating a knock-on effect (putting solar panels on your roof is contagious , for example).

For most of us in America, our most effective individual options for cutting our carbon footprints are: trading in our gas guzzler for a more efficient (good), hybrid (better), or electric (best) car; driving and flying less; eating less beef and lamb; and buying green electricity, installing solar panels, and making concerted home efficiency improvements. If you can only do one, make it trading in your car or eating less beef. Another important but less obvious option is to divest our savings and pensions from fossil fuels, which also sends a strong social signal .

On average, these actions would together cut your carbon footprint roughly in half.

This carbon footprint calculator can help you make these cuts. To figure out the best car to get, use this app , based on research by one of us. To find fossil fuel-free investment funds, go here .

If you find this guide useful, please share it. Then, let’s get to work!

Geoffrey Supran is a postdoctoral researcher in the Institute for Data, Systems, and Society at MIT and in the Department of History of Science at Harvard University. He has a PhD in Materials Science & Engineering from MIT.

Ploy Achakulwisut is a PhD candidate in Atmospheric Science at Harvard University.