For more than 50 years, Earth Day has been celebrated on April 22 across the country and the world. While it is not a federally recognized holiday, people celebrate Earth Day through action for, awareness of and education about the Environmental Movement.

I like to think that Earth Day and I have a personal relationship. I remember participating in the first one as a demonstrator on April 22, 1970. At that time, there was no Clean Air Act, no Clean Water Act and no Environmental Protection Agency. There were no legal or regulatory mechanisms to protect our environment.

I was living in Wisconsin at the time, the home state of Senator Gaylord Nelson, the founder of Earth Day. Thirty-four years later, I had the great honor of meeting and working with him on a photo shoot and handing him a white pine sapling, a tree that he had requested to hold. Sixteen years after that, I worked with Tia Nelson, his daughter and the climate change program director for the Outrider Foundation—an organization that uses digital media to build understanding of and inspire action for the Earth—on an article for this blog.

So, every April 22 since 1970 has been a special day for me, and I take note of every annual theme. The one for Earth Day 2023 is “Invest in Our Planet.” I think it’s one of the best yet.

Why? Because now science is giving us a good reason and an excellent way to do just that.


The 1970 Clean Air Act is a federal law that regulates air emissions from mobile and stationary sources. Among other things, this law authorizes the Environmental Protection Agency to establish National Ambient Air Quality Standards to protect public health and to regulate emissions of hazardous air pollutants.

The reason: the Paris Climate Agreement goal is still possible

The Paris Climate Agreement is a legally binding international treaty on climate change. It was adopted by 196 parties at the United Nations Climate Change Conference (COP21) in Paris, France, on December 12, 2015. It entered into force on November 4, 2016. Its overarching goal is to hold “the increase in the global average temperature to well below 2 degrees Celsius (3.6 degrees Fahrenheit) above preindustrial levels” and to pursue efforts “to limit the temperature increase to 1.5 C (2.7 degrees F) above preindustrial levels.”

However, in recent years, world leaders have stressed the need to limit global warming to 1.5 C by the end of this century. That’s because the United Nation’s Intergovernmental Panel on Climate Change (IPCC) indicates that crossing the 1.5 C threshold risks unleashing far more severe climate change impacts, including more frequent and severe droughts, heatwaves and rainfall. To limit global warming to 1.5 C, greenhouse gas emissions must peak before 2025 at the latest and decline 43 percent by 2030.

The United Nations states that the Paris Climate Agreement is a landmark because, for the first time, a binding agreement brought all nations together to combat climate change and adapt to its effects. And happily, according to a study published in the journal Environmental Research Letters in February 2022, the 2015 Paris Climate Agreement goal is still within reach.


The 1972 Clean Water Act established the basic structure for regulating discharges of pollutants into the waters of the United States and sets quality standards for surface waters.

In order to explore and plan for possible futures, the climate research community uses scenarios: forecasts of how the future might evolve based on factors such as projected greenhouse gas emissions and different possible climate policies.

The most used scenarios, called the Representative Concentration Pathways (RCPs), were developed by the IPCC starting in 2005. The Shared Socioeconomic Pathways (SSPs) that followed, starting in 2010, were meant as an update. Together, the two sets of scenarios were used to create the IPCC’s Sixth Assessment Report.

The authors of the Environmental Research Letters study started with a total of 1,311 climate scenarios from which the climate research community selected the 11 RCPs and SSPs. They then compared the scenarios to the projected 2005–2050 fossil fuel and industry carbon dioxide emissions growth rates most consistent with real-life observations from 2005–2020 and projections to 2050. The number of scenarios which most closely matched up to data from the past 15 years and subsequent emissions projections ranged from less than 100 to almost 500, depending upon the method applied. These scenarios represent what futures are plausible if current trends continue and countries adopt the climate policies they have already announced to reduce carbon emissions.


The Environmental Protection Agency was created on December 2, 1970, as part of the response to growing public concern and a grassroots movement to “do something” about the deteriorating conditions of our air, land and water.

The scientists found that a subset of climate scenarios from the IPCC most in line with recent data and International Energy Agency forecasts to 2050 project between 2 and 3 C (3.6 and 5.4 degrees F) of warming by 2100, with a median of 2.2 C (3.96 F). In comparison, some implausible, worst-case scenarios have projected as much as 4 or 5 C (7.2 or 9 F) degrees of warming by the end of the century.

This news is cautiously optimistic with respect to where the world is today compared to where we thought we might be. That means that the two-degree target from the Paris Climate Agreement remains within reach.

There is a caveat, though: because IPCC scenarios haven’t been updated for many years, the scientists say there are some futures which are plausible but haven’t yet been envisioned. And those could be more optimistic or more pessimistic.


The global transportation sector is a major air polluter. In 2020, it produced approximately 7.3 billion metric tons of carbon dioxide emissions. Passenger cars were the biggest source of emissions that year, accounting for 41 percent of global transportation emissions.

However, the analysis joins a growing consensus of independent groups around the world whose work suggests that the most extreme climate scenarios are unlikely to occur in this century and that midrange scenarios are more likely. The IPCC Sixth Assessment Report also notes that the likelihood of high emissions scenarios is considered low. Why are these worst-case scenarios now less plausible? Mostly because they were all developed more than a decade ago, and a lot has happened since then. For example, renewable energy has become more affordable and, thus, more common faster than expected. Climate scenarios also tend to overestimate economic growth, especially in poor countries.

The researchers say that their study points out the need for these scenarios to be updated more frequently. Scientists may be using a 2005 scenario when a 2022 perspective is needed. But the authors also stress that 2 C (3.6 F) of warming will still take a dramatic toll on the planet, and this is no time for complacency. Data shows that the average global temperature has already risen around 1.1 to 1.2 C since industrialization, and the planet could reach 1.5 C of warming above preindustrial levels in a decade.

The way: the Carbon Takeback Obligation could work

Imagine a single policy, imposed on one industry, which would, if enforced consistently, stop fossil fuels causing global warming within a generation. The Carbon Takeback Obligation could do just that. It requires fossil fuel extractors and importers to dispose safely and permanently of a rising fraction of the CO2 they generate, with that fraction rising to 100 percent by the year of net-zero. This would include carbon dioxide generated by the products they sell.


In 10 years, the price of solar electricity dropped 90 percent. Clean energy has already passed its economic tipping point. Since 2019, it has been cheaper to build and use a combination of renewables, such as solar and wind, than to build new natural gas plants.

A groundbreaking study from the University of Oxford and the University of Edinburgh, published in the international energy journal Joule in October 2021, explores the economic implications of imposing a carbon takeback obligation on the global fossil fuel industry and shows it provides an affordable and low-risk route to net-zero emissions, particularly if complemented by conventional measures to reduce fossil fuel demand. Despite the perceived high cost of carbon dioxide capture and storage, the cost to the world economy of a Carbon Takeback Obligation, even if entirely passed on to fossil fuel consumers, is no higher than the cost of mitigation in conventional scenarios meeting similar goals.

According to the study’s authors, investment in carbon dioxide capture and geological storage has, to date, been dependent on state subsidies and consistently far below what is required to meet the Paris climate goals. Carbon Takeback provides the fossil fuel industry with the strongest possible incentive to make amends: survival.

An independent expert in carbon capture and storage who reviewed the work commented that a Carbon Takeback policy as proposed in this paper will provide a safety net to make sure we achieve net-zero emissions even if we don’t manage to reduce the use of fossil fuels quickly enough. It extends the responsibility of producers to take care of the waste generated by using their products. The polluter pays to clean up, and the costs are included in the product price.


I hope your Earth Day 2023 will have a personal meaning. How do you intend to invest in our planet?

The time: it’s now doable

The Earth Day 2023 campaign highlights how investing in our planet is the most sensible option for our families, our finances and our futures. High upfront costs are often given as a reason not to invest in renewable energy. However, in the past 10 years, the costs of clean energy technologies have declined dramatically. Wind-power costs have decreased by half, solar panels by 90 percent and batteries by even more. Wind and solar now produce 10 percent of the world’s electricity and are adding 1 to 2 percent every year. The United States spends an estimated $37.5 billion on fossil fuel subsidies yearly, money that could be going to research and development of renewable energy projects.

Only a few years ago, even optimists would have considered zero emissions unrealistic. Today, two-thirds of the world’s polluters have committed to net-zero emissions by mid-century. Investing in clean energy has the potential to do most of the work in reducing the world’s greenhouse gases to zero.

But like Earth Day for me, your Earth Day should be personal, too. How can you, invest in our planet? Here’s a list of 52 ways.

Happy Earth Day 2023, and here’s to finding your true places and natural habitats,