The quote from page 183 of Bill Nye's book which says "... 2 decades earlier" seems to mean 2 decades earlier than the year 1993. I think that because of the following. The quote on page 183 about the temperatures of Venus and of Earth is of what Bill Nye says he discussed in a book he wrote in 1993. Furthermore, a Wikipedia article about Bill Nye says he attended Cornell University from 1973 to 1977, and it says that while at Cornell Bill Nye took an astronomy course taught by Carl Sagan.
Regarding Vidqun's question of "Why is the mean temperature of Mars -60 degrees Celsius?", despite CO2 being about 96.5% of total gases, that answer should be obvious to those who researched the matter. It is obvious to me. It is because the total amount of gases on Mars is minute. The total amount of atmosphere of Mars is only about 1 percent of that of Earth. If the amount was the same as that of Earth it would be a much warmer planet than it now it. Scientists say that Mars used to have much more atmosphere but that it lost most of it, largely because its gravity wasn't strong enough to hold onto it. They also say that liquid water used to cover much of the surface of Mars and that Mars used to be much warmer than it is now.
Regarding Venus, it has vastly more total atmosphere than Earth. Scientists say that Venus used be much more like Earth - even possibly habitable, but that it later experienced a runway greenhouse effect! https://climate.nasa.gov/news/2475/nasa-climate-modeling-suggests-venus-may-have-been-habitable/ says the following.
"Venus today is a hellish world. It has a crushing carbon dioxide atmosphere 90 times as thick as Earth’s. There is almost no water vapor. Temperatures reach 864 degrees Fahrenheit (462 degrees Celsius) at its surface.
Scientists long have theorized that Venus formed out of ingredients similar to Earth’s, but followed a different evolutionary path. Measurements by NASA’s Pioneer mission to Venus in the 1980s first suggested Venus originally may have had an ocean. However, Venus is closer to the sun than Earth and receives far more sunlight. As a result, the planet’s early ocean evaporated, water-vapor molecules were broken apart by ultraviolet radiation, and hydrogen escaped to space. With no water left on the surface, carbon dioxide built up in the atmosphere, leading to a so-called runaway greenhouse effect that created present conditions."
See also https://www.washingtonpost.com/climate-solutions/2020/03/20/runaway-greenhouse-effect-turned-venus-into-hell-could-same-thing-happen-here/ which says in part the following about Venus.
'Once upon a time, around small yellow sun, there existed a world with a rocky surface and a molten core. It harbored water and may even have been hospitable to life.
Then the planet got hot -- really hot. Its atmosphere filled with heat-trapping gases. Water evaporated into its atmosphere and then was lost to space. Whatever mechanisms the planet may have had for balancing its climate were broken. Nothing, not even a robot, could survive there.
This is not a scenario from a science fiction novel about climate change (or the director’s cut of Wall-E). It’s what scientists say really happened to a world in our own solar system: Venus.
... Now Venus is the poster child for the “runaway greenhouse effect," a testament to the way a planet can change when the cycles that balance its climate are broken. The temperature at its surface is more than 850 degrees Fahrenheit -- as hot as a self-cleaning oven. The crushing pressure of an atmosphere thick with sulfuric acid clouds is as intense as what you’d experience half a mile beneath the ocean on Earth. If that wasn’t enough to kill you, breathing air composed of 96 percent carbon dioxide would do the trick.'
Regarding Vidqun's question of "Who pays Bill Nye's salary?", I see no significance to that in determining if that means Nye isn't really concerned about climate change being a huge danger to humankind or not. Many people take jobs in particular fields because those fields address matters which are important to them, instead of choosing them solely as a way to make money. For example, for a number years I had an online home-based business which sold solar electric modules. I chose to make money from that, rather than from something else instead of it, because I was (and am still) very greatly concerned about the environment and the environmental need for humankind to switch to from fossil fuel energy sources to renewable energy. My efforts to make money from the sale of solar electric modules did not cause me to be dishonest about the environmental importance of solar power and it did not cause me to be dishonest about the need to protect the environment, and it did not cause me to become dishonest about anything else.
Regarding where Bill Nye made and makes money from employment, he was host of the science education television show called Bill Nye the Science Guy from 1993–1999, and he makes money from the books he wrote which advocate science. Currently he is CEO of The Planetary Society, an American internationally-active non-governmental nonprofit organization. I don't know how much money, if any, he makes from that nonprofit organization. https://en.wikipedia.org/wiki/The_Planetary_Society says "The Society is dedicated to the exploration of the Solar System, the search for near-Earth objects, and the search for extraterrestrial life.[4]" The organization thus does seem to be about climate change.
https://www.latimes.com/opinion/op-ed/la-ol-patt-morrison-bill-nye-science-20170719-htmlstory.html quotes Bill Nye as saying the following.
'One’s intuition about climate change is not as good as facts about climate change.
It just sounds like people are scared. It just sounds like people are afraid. And the people who are afraid in general — with due respect, and I am now one of them — are older. Climate change deniers, by way of example, are older. It’s generational. So we’re just going to have to wait for those people to “age out,” as they say. “Age out” is a euphemism for “die.” But it’ll happen, I guarantee you — that’ll happen.'I hope that Bill Nye is right in thinking that the majority of climate change deniers are older people and that as result eventually there will be virtually no more climate deniers, since climate change is for real and urgently needs to recognized as such by the vast majority of adult humankind! Poll results say that Bill Nye is right about what age group primarily denies climate change. Note that https://www.pewresearch.org/fact-tank/2021/05/26/key-findings-how-americans-attitudes-about-climate-change-differ-by-generation-party-and-other-factors/ says the following regarding people in the USA
"
Younger generations in the U.S. are especially likely to express an interest in addressing climate change – and to say they have personally taken some kind of action to do so. About a third of Gen Zers (32%) and 28% of Millennials say they’ve done something in the past year to address climate change, such as donating money, volunteering, contacting an elected official or attending a rally or protest. And two-thirds of Gen Zers, as well as 61% of Millennials, say they’ve talked with friends or family about the need for action on climate change in the past few weeks. Smaller shares of Gen X and Baby Boomer and older adults say they’ve done these things.
Younger generations are also more likely to engage with climate change on social media: 45% of Gen Z and 40% of Millennial social media users say they’ve engaged with climate-related content in some way, such as by interacting with or sharing a post about the need for climate action or following an account focused on the cause. About half as many social media users who are Baby Boomers or members of older generations report doing the same.
A majority of Gen Zers (56%) and Millennials (57%) support a move to phase out gasoline-powered vehicles, compared with smaller shares in older generations. Younger generations are also significantly more likely than older ones to support phasing out the use of oil, coal and natural gas entirely, though about half or more across all generations favor using a mix of fossil fuel and renewable energy sources going forward."