I accepted an invitation to speak at the San Jose People’s Climate March on April 29th, 2017 and I have reproduced what I said below. *Note that I do not necessarily endorse the People’s Climate March policy platform and I would not wish to defend any statements other than my own*.

Good afternoon. My name is Patrick Brown and I am a climate scientist.

I would like to say a few words today in the name of celebrating science – and in defense of science’s ability to inform society on issues of critical importance – like climate change.

Now as most of you know, the primary agent of current climate change is increasing levels of carbon dioxide from the burning of fossil fuels.

I want you to think about whether or not you would know this without modern science. Could you surmise this on an intuitive level?

Carbon dioxide is a colorless, odorless, tasteless gas. But despite its invisibility to our senses, the methods of science have allowed us to identify its existence and eventually measure it in the atmosphere.

The methods of science also allowed us to figure out that carbon dioxide contributes to what would become known as the greenhouse effect, and thus it can affect global temperatures.

When we began burning fossil fuels to power our societies, there was no intuitive reason to think that emissions of this invisible gas might be able to affect the global climate.

There was no intuitive reason to think that burning coal in Pennsylvania could contribute to sea level rise in Sydney….Yet we now know that this is the case.

In order to discover truths about our world that are beyond our intuition, we need to allow science to flourish freely.

let’s imagine for a moment that across the world, free scientific inquiry had been overtly suppressed over the last several centuries.

If free scientific inquiry had been suppressed, we wouldn’t be able to measure the temperature of the planet:

We wouldn’t know that the atmosphere is warming (as measured by a global network of weather stations, satellites, and weather balloons).

We wouldn’t know that the oceans are warming (as measured by ships, buoys, and satellites)

We wouldn’t know that the Earth’s ice is melting: sea ice, alpine glaciers and the Greenland and Antarctic ice sheets

And we wouldn’t know that global sea levels are rising

If we had accepted the stifling of free scientific inquiry we wouldn’t be able to ask questions about the future.

We would have no idea, for example, that if we were to burn all available fossil fuels, that would be sufficient to melt the entire Antarctic ice sheet over the next several thousand years – 6 million cubic miles of ice.

This would be enough melting to dramatically reshape the world’s coastlines.

This location where we stand would be under water, it would turn the California Central Valley into an inland sea, and it would It would essentially remove Florida from the map.

If we accepted the stifling of science we wouldn’t know that the rates of global warming under a ‘business as usual’ future are at least 10X faster than any global climate change experienced over the past 65 million years.

Finally, if we had stifled free scientific inquiry, we wouldn’t know how difficult it will be to limit global warming: We wouldn’t know that in order to simply stabilize global temperatures, we need to reduce carbon dioxide emissions by 80%.

Now, fossil fuels are not all bad – there is a reason that we have been using them. Everything that we materially value requires energy and historically, fossil fuels have provided the most affordable way to produce that energy.

This has led to successes that should not be ignored: large reductions in infant mortality, reduced rates of many horrible diseases, reduced poverty at a global scale, and robust increases in average lifespan.

But If science had been stifled, we would only know about the salient benefits of fossil fuel use and we would be totally ignorant to the dangers of burning fossil fuels.

Now, science has no “unquestionable truths” and as a scientist, I spend a great deal of my time questioning what other scientists think.

This skeptical aspect of science is precisely why we have so much confidence in scientific conclusions: Our confidence in the conclusions comes from the conclusions surviving challenge after challenge.

Thus, I have no problem with anyone challenging any scientific conclusion, including the findings that I just laid out.

BUT…but…If you want to question a scientific conclusion, you need to have good evidence (Preferably written up in a scientific paper and submitted to a scientific journal for peer review).

So I DO have a problem, when politicians or anyone else in power, have the hubris to cavalierly dismiss scientific conclusions out of hand – essentially dismissing hundreds of millions of cumulative hours of careful scientific work – simply on intuition.

and yes, referring to global warming a “Chinese hoax” fits into this category.

To conclude, I want to emphasize that free scientific inquiry, unencumbered by ideological opposition of those in power, is what has made it possible for us to understand the non-intuitive dangers of fossil fuel burning.

Namely that an invisible gas called carbon dioxide, that is produced from burning fossil fuels, is the primary driver of current climate change and that without curbing our emissions of this gas, we will experience rates of global change that are truly exceptional in the geologic record.

Therefore, any politician who engages in the suppression of inconvenient scientific conclusions or who has the hubris to dismiss those conclusions on intuition is being woefully irresponsible.

And that irresponsibility should be punished by damage to their reputations and a price paid at the ballot box.