[Imogen Game]

Imogen Game  asked the Naked Scientists:
   
Dear The Naked Scientists,
 
I'd like to start by saying that I'm a huge fan of your show - I listen to literally every one of your podcast feeds and have done for a few years now.

I started listening to you guys when I was still in high school and you gave me lots of interesting anecdotes about all the latest science with which I regularly baffled my family and friends, who thought me extremely nerdy!

You guys make science so accessible - I regularly attempt to navigate public science journals and get lost in jargon and things I don't understand!
 
I have something that's been puzzling me for some time now, and I was wondering if you could give me your opinions on it. I am a massive climate skeptic - I find it really hard to believe that anthropogenic CO2 emissions could possibly have the kind of impact many mainstream scientists claim it does.
 
So this is my question for you:   If CO2 comprises 0.038% of the atmosphere, and only 3% of that is from anthropogenic sources, how can the tiny incremental increase in atmospheric composition that we've caused over time, really create substantial temperature change? Why is the evidence for sunspot activity not cited more often as a cause of recent climatic changes? Surely the impact of sunspots would vastly outweigh the tiny increase in the greenhouse affect? I would love to hear your explanations for this - it would be really helpful to me in my grappling!
 
Thanks very much! :-)
 
Imogen Game (Sydney, Australia)

What do you think?

[CliffordK]

So this is my question for you:   If CO₂ comprises 0.038% of the atmosphere, and only 3% of that is from anthropogenic sources,

You have your numbers off a little bit...
CO₂ comprises about 0.038% of the atmosphere.

But, the anthropogenic component is increasing from about 0.028% to about 0.038%, or about 30%.

The significance of the carbon dioxide is still being debated.  However, at certain IR frequencies, even the 0.038% CO₂ is sufficient to absorb 100% of the outgoing IR light irradiation.  So, increasing the concentration of CO₂ lowers the elevation at which this absorption occurs, as well as increasing the number of times the light is absorbed, and radiated on its outward path.

Certainly solar irradiation is also important, and one of the major complaints about the current anthropogenic global warming theories is that they seem to base too little on natural climate cycles.

[yor_on]

 Carbon Dioxide in the Ocean and Atmosphere.

[syhprum]

I understand that 55 million years ago the proportion of CO2 in the atmosphere was 6500 ppm and we all survived so why are we all panicking today as it creeps past 400 ?

[chiralSPO]

I understand that 55 million years ago the proportion of CO2 in the atmosphere was 6500 ppm and we all survived so why are we all panicking today as it creeps past 400 ?

The major issue is not the concentration of CO₂ per se (although, one important thing to note, is that a significant portion of our cities would have been underwater in the Cretaceous: https://wattsupwiththat.com/2013/09/26/study-the-late-cretaceous-period-was-likely-ice-free/). The major problem that people are (or should be) concerned about is the rate at which the concentration is changing.

The composition of the atmosphere does change, but it typically does so on a geological timescale (hundreds of thousands to millions of years). Anthropogenic emissions have changed the concentration of CO₂ more in the last 250 years than the previous million years of natural variations.

To get an idea of the disparity between the extent of natural variation over the last million years and what has happened just recently see here:

https://www.epa.gov/climate-indicators/climate-change-indicators-atmospheric-concentrations-greenhouse-gases

This is also a useful tool for wrapping our heads around the abruptness of the change (in temperature):
https://xkcd.com/1732/

Unfortunately, forests cannot just uproot and move a few thousands miles North on a century's notice. Other evolutionary adaptions also take time (thousands of years or more, rather than decades). It appears that every time the atmospheric composition has changed very rapidly there has been a major extinction event.

Will climate change destroy all life on Earth? Almost certainly not.
Will it cause most species to go extinct? Possibly.
Will it be bad for the economy? Yes.
Will humans survive it? Probably.
Will reducing the rate of CO₂ emissions reduce the hardships on our species and other macrofauna? Absolutely.

[alancalverd]

Will it be bad for the economy? Yes.

Or no. The clearance of ice from the north pole will radically reduce shipping transit times and make bulk surface transport (slow moving, fast handling) competitive with air cargo (fast moving, slow handling) in the northern hemisphere.

[chiralSPO]

A substantial portion of major cities (and now that you mention it, all ports for shipping) are costal cities, which are going to require very expensive responses to sea-level rise. Whether building levies and canals and pumping stations, or actually relocating, there is no cheap way to deal with a seaside metropolis transitioning to being at or below sea level... Note that a city only needs to be "below" sea level a few times a year for the economics of doing nothing to be untenable--storm surges, high tides, substantial rains and other factors can cause coastal flooding.

My very US-centric view of this is focused on:
New York City, Boston, Washington DC, Miami, Seattle, Houston, New Orleans, Baltimore...

For other countries, consider:
London (which is also sinking), Singapore, Mumbai, Shanghai, Guangzhu, Osaka, Bangkok, Manilla, Jakarta, Amsterdam, Tel Aviv, Cairo, Dhaka, Venice...

And then there are issues of migration of arable land (some places are getting too dry, and some are getting too wet). Our farms and farmers can move, but at what cost? (plus given the pushback immigration gets these days, I can't imagine that the political costs will be insignificant...)

[chiralSPO]

And don't just take my word for it, those who have much better understanding believe that most ports will be in a very bad way by 2100:

https://link.springer.com/article/10.1057/s41278-018-0114-z

[Bored chemist]

Will it be bad for the economy? Yes.

Or no. The clearance of ice from the north pole will radically reduce shipping transit times and make bulk surface transport (slow moving, fast handling) competitive with air cargo (fast moving, slow handling) in the northern hemisphere.

People pay more for air transport because, for many things, it's simply "better".
So it's far from clear that offering a "cheap, but bad" option will greatly benefit the economy.
Killing the polar bears so you can ship goods from the UK to the far end of Russia doesn't seem a very good deal to me

[ConnorGunning]

And it's not a very good deal.
There's article on national geographic about how we could fix our situation, but it's not that simple, is it?