If you're a child of the 1990s, then odds are you know Bill Nye as "the Science Guy." But he hasn't slowed down since his wildly popular children's television program - he's continued to advocate for the importance of science in all of our lives, most recently as CEO of the Planetary Society.

His work has also centered on addressing one of the most pressing issues today: climate change. For Earth Day, Nye shares his memory of attending the very first Earth Day in Washington DC in 1970, the tools we really need in the climate-change fight, and why we should always remain optimistic.

Earth Day was organized in Washington. I rode my Schwinn bicycle - at that point, I believe I had a Schwinn Continental that was green - and I rode it down and I locked it to a flag pole at the Washington Monument. I think if you tried that now, they'd probably arrest you. Anyways, they had a big stage, and they had a lot of speakers, and at that time, people were concerned about pollution. That was the thrust of Earth Day; there was a big campaign about not littering. So that idea of individual action being very important dates back to that time, at least for me.

But I'll say as I've said quite a bit in the last year: individual action isn't going to do it. When it comes to Climate change, it's going to take much bigger ideas, much more focused efforts. So I just like to remind people - I like to disabuse them of the idea that if we just recycle our water bottles, then everything will be fine. That's not true. We need renewable energy, clean water, access to the internet for everyone.

Because of the atmosphere, we all share the same air. So if each of us adds more methane, more natural gas, more carbon dioxide to the air, it's going to affect everyone else in the world. A strange and surprising but irrefutable truth. So what little things can you do to address climate change? Everything. Carpool, don't throw plastic bags away, don't squander plastic water bottles, recycle aluminum, combine your errands. When you go to choose a car, take the environment into account. That's a huge effect that each of us has. And if you are a homeowner, consider investing in so-called weatherization - new windows, for example. These are Big Investments. Replacing the windows in my small house in Los Angeles, back when I did it, cost over $20,000. Nowadays, I imagine it would be about $30,000, the same as buying a car. But it means that your house loses less energy for the next 30 years. So that's an example of individual action that's actually a big investment that can affect everybody.

But more than that, when people say to me, "Bill Nye the Science Guy, what can I do about climate change?" I say, "Vote! Vote!" That is where we're going to make changes, by putting lawmakers in place who are concerned about climate change and will pass legislation that will address it.

Another thing: we have to be optimistic. If you're not optimistic, you're not going to get anything done. If you go into a game - a sports contest or a card game - if you think you're going to lose, well, then, there's a good chance you'll lose. It doesn't mean you have to be irrational or ignoring the scale of the problem, but it does mean you have to go at it like we're going to solve this problem.

The example I give people all the time is World War II. My parents were both veterans of World War II. My dad was a prisoner of war for almost four years, and my mother was one of the women recruited to work on the Enigma code and then later the Japanese naval codes. And everybody was anxious. Everybody was very scared about what was going on in Europe and in Asia. So they got something done. We've been there, and we've solved these big problems before. And what it takes, again, is leadership, and that's where voting comes in.

The other thing I tell people about doing something about climate change is talking about it. If it were in public consciousness as much as some other very important issues are, we would be addressing it.

Now, when it comes to the United Nations' goals, let's simplify and think about clean water; renewably produced, reliable electricity; and access to the internet for everybody in the world. If we can do those three things, we could change the world for everyone. And the big background idea is raising the standard of living for women and girls. When you raise the standard of living for women and girls, everybody is better off. Everybody's quality of life is higher. When women have a higher standard of living, they have fewer kids, and the kids they do have have more resources, they have a higher quality of life, they're more productive, and they're going to come up with the policies and technologies that will change the world.

We are also on the verge, I think, of having nuclear-fusion technology here on the Earth's surface without importing a star. And if we can pull this off, this will change the world. And I think achieving nuclear fusion with a usable, scaleable technology is going to take big investments - the same way we had big investments in World War II. So I encourage everybody - not that we don't have to do everything all at once - but we may very well be living at a time when this huge problem is solved, and then in the next 30 years or so, we could have electricity for everybody. But it's going to be, as we say in sailboat racing, a "near run thing."

Are these emerging technologies and climate policies going to be put in place fast enough to affect enough people on Earth to make it something to be proud of? The Earth is going to be here no matter what people do. If we kill ourselves, I don't think the Earth will be the slightest bit concerned. What we want to do is preserve the quality of life for as many people as possible, and in order to do that, we need to get to work as fast as we can.

- As told to Lena Felton