Brian Cox on Q&A

I forget how many Aussies we have on the forum, but came across this video while pretending to do lab work today. Highly recommend watching it all the way through, but the part that made me want to share this starts around 11 minutes in.

 

question from the audience, 'can you provide evidence, not just opinion that there is a human component to climate change?'
moderator, "can you provide evidence that there is a human component to climate change?'
brian cox, 'yes I could'

then he goes on just to report temperature measurements and says they are alarming.

still waiting for evidence that there is a human component to climate change.

 

In lab currently (and actually doing work now), but will go into this once I'm back in my flat.

 

Right, so your statement is just vague enough that I'm going to have to make a couple assumptions about the kind of data you're looking for. I'm going to assume that you accept the body of evidence that Earth's climate is changing significantly faster than background rates. I'm also going to assume that you have at least a layman's understanding of science, but also that you're not an expert. It's possible I'll overestimate what the 'layman' understanding is, so if I talk about a concept that's difficult to grasp, tell me and I'll try and break it down.

With the above assumptions, I take it that you're looking for evidence that human activity is responsible for the bulk of the observed changes, and I'll be presenting this post with that in mind.

Let's take a step back first and examine what causes the climate to change. The climate of Earth is the result of a really rather complex range of factors. The layout of the continents, positions of the oceans, degree of volcanic activity, and even orbital cyclicity all play a part in controlling what the climate is like. The influences can be felt at global, regional, and local scales. To use an example, our current ice caps only began to form when Antarctica moved to its current position, and only became extensive (and permanent) when the circum-polar current cut off the Antarctic Sea from the rest of the worlds oceans. We know that Antarctica has been hovering around the southern pole since the Mesozoic, but it was still connected to other land masses at the time. Those landmasses were Australia and South America, and the connection is the reason why there's shared fauna between the continents (most notably Marsupials). Australia broke away first, followed by South America. The opening of the Drake Passage signalled the severing of the last piece of land connecting Antarctica to South America. This happened around the Late Eocene (Scher and Martin, 2006) [1]. Most models suggest that this event was the main trigger for ice formation, and the subsequent cooling of the climate throughout the rest of the Palaeogene and Neogene.

The isolation of Antarctica gives a nice example of several kinds of climactic shifts brought on by geological activity. On a local level, the water became a lot colder, and therefore more pre-disposed to holding nutrients. On land, a frozen landscape became the new norm, forcing terrestrial life to take on strategies that brought them to what we see in the modern day in response to the encroaching ice. At a regional level, the passage around Cape Horn became notably more turbulent thanks to the circum-polar current. The current also acted (and acts) as a barrier to the mixing of bodies of water, and means that there's a very clear dividing line between southern ocean fauna's and Antarctic fauna's. Finally, at a global level, the formation of the ice cap lead to a progressively drier climate. With water being locked away in ice, the tropical hothouse typical of Earth since the Jurassic began to give way to more temperate icehouse conditions, with extensive rainforests giving way to savannah's in many parts of the world.

Now, all of these shifts weren't instantaneous. They took many millions of years to reach the positions we see in recent times. Environments tend to have inertia, it's why a desert can continue to exist in conditions that could potentially support scrubland. The isolation of Antarctica also wasn't the only factor at play. At such a long time scale, it would be foolish to try and claim that to be the case. The raising of the Himalaya's almost certainly played a large role as well. The uplift of mountain ranges has two-fold impacts on the climate (Ruddiman, 2013) [2]. The first is the simple physical interposition of the newly created range warping local atmospherics. Most commonly, this creates a rain shadow as the air is stripped of moisture as it passes over a mountain range, but in the case of marine ranges, it can also disrupt ocean currents. More indirectly, the process of raising a mountain range causes a great degree of weathering as fresh rocks are exposed to the atmosphere. The chemical weathering of silicate rocks in particular strips CO2 from the atmosphere (Brady, 1991) [3]. Lowered atmospheric CO2 (pCO2) leads to lowered global temperatures, as indeed you would expect to happen when removing greenhouse gases from the atmosphere.

So we have examples of how to cool a climate, both through purely physical means, as is the case with Antarctica, and through chemical means via. increased rates of weathering. What about warming it up? I've already mentioned greenhouse gases, and these are indeed the primary means (sustained asteroid bombardment will also do it, but that's not been relevant for several billion years now). The most predominant greenhouse gas in the atmosphere right now is water vapour. However, it's unevenly distributed throughout the atmosphere. The highest concentrations are in tropical and sub-tropical regions, areas which already receive a great deal of solar energy. Rainforests are probably the most famous example, and are indeed regions with such a high concentration of water vapour that you get rain almost every single day, year round. So why aren't we more concerned about water vapour? Well, its effects are only felt in regions that have already adapted for high tolerance of high water vapour concentrations. Its lack of a global distribution means that particularly arid regions, such as the polar ice caps, or mountain tops, see little influence from it.

So what's the next main greenhouse gas? CO2. Unlike water vapour, CO2 is not primarily limited to the tropics, and has a pretty even spread around the globe. While there probably are regions that have slightly higher or lower concentrations (I've not checked to see if this is true or not), there's no atmospheric forcing that keeps it out of arid regions in the same way as water vapour. We can see the impacts of an increase in pCO2 by looking into the geological record. During the Cretaceous, we can identify a trio of relatively low pCO2 values (<400 ppmV) within the Early and Late Cretaceous, linked to transitive glacial episodes, and an average of <1000 ppm and ~800 ppm in the Early and Late Cretaceous respectively. The pCO2 values were highest during the mid-Cretaceous, with an average of 1000-1600 ppm, and two distinctive spikes estimated to be as high as 2500 ppm (Hong and Lee, 2012) [4]. The high values have been tentatively linked to geological outgassing resulting from volcanic activity. Importantly, though, the pCO2 can be correlated quite closely with the changing temperatures through the Cretaceous.

So, now that we've established how to warm up and cool down the climate, let's look at the impacts on the environment. You'll notice that the Cretaceous variation is significantly broader than the currently observed variation (from ~260 ppm pre-industrial, to ~400 ppm now). And, aside from the famous meteor impact that heralded the end of the Mesozoic, there weren't any mass extinction events during the Cretaceous. So why is the scientific community so concerned about modern climatic shifts? It all comes down to a question of how fast the change is happening. As I've alluded to, climatic change typically takes millions of years to take effect. The changes seen through the Cretaceous were not overnight events, and as such the organisms of the time were (mostly, there's always a constant background extinction rate) able to adapt to the changes and continue on as before. If the climatic change is rapid, however, we often see dramatic faunal turnover and, in the most extreme cases, mass extinction events. The problem with examining the impacts of a rapidly increasing pCO2 level is that it's not really something that happens in nature. As such, we only really have a couple of events that could be compared. The first is the output of the Deccan Traps at the end of the Cretaceous, with the per annum estimated output range being 0.01716 to 0.04224 gigatonnes per year, with a total outgassing of 22000 gigatonnes by the end of the event (McClean, 1985) [5]. The reason for the range of estimates is simply due to uncertainty over the duration of the event, with a duration range of 0.53-1.36 Million years proposed (the paper I'm referring to is old, this may not be entirely accurate, but it suffices for my point). While fast, this is still several orders of magnitudes slower than the rates we're seeing right now, and indeed Ridgwell and Schmidt (2010)[6] point to the need for an event occurring on a time scale of <10 kyr (thousand years) being necessary to see biotic responses. So we need a faster event.

That takes us to the Palaeocene-Eocene Thermal Maximum (PETM). This is an event, appropriately enough, at the Palaeocene-Eocene boundary. The PETM, as the name suggests, saw the highest temperature spike within the Palaeogene. The event is associated with a massive increase in pCO2. The origin of the CO2 pumped into the atmosphere is uncertain, with methane hydrates being the current favoured culprit. Ridgwell and Schmidt use two models of the PETM, one with a release of 6,840 Gigatonnes over 10kyr, the other is a release of 2180 Gigatonnes over 1kyr. Both are based on pre-existing studies, and account for different possible release methods. Unsurprisingly, both models have pretty devastating impacts for the ocean, with acidity spiking alongside temperature. The 1kyr release is particularly bad, and predicts the longer recovery time. Both models are true to what the geological record tells us. At the time of the PETM, calcareous fossils disappear from all but the very shallowest locations, indicating a time of extreme stress for the organisms. The recovery of life takes several hundreds of thousands of years after the event, with the deepest portions of the ocean taking the longest to recover to pre-event diversity.

Now, the benefit of using the models above is that one of them, the 2180 Gigatonne release over 1kyr, is directly comparable to one of the IS92a emission scenario's, with a linear reduction to a total release of 2180 Gigatonne after 2100 following (Emissions Scenario's, 2000) [7]. Ridgwell and Schmidt applied the model they used for the PETM to this modern estimate, and found a similar scenario. We have a slightly better recovery estimate thanks to some quirks of modern geology, but they still predict warming of the deep ocean to create an unstable stratification, causing upset throughout the marine ecosystem just from thermal dynamics. The additional consideration of acidification worsens the predictions considerably, as it hits broad swathes of the marine ecosystem (most notably, planktic foraminifera and corals, the former of which I'm currently carrying out a masters project on). We can already see the impacts of this in the mass bleaching and dying of many reef systems, particularly the Great Barrier Reef (without looking it up, I believe a good ~66% is bleached at this point, and I wouldn't be surprised if that number was higher).

So, we know how the Earth is warming, and we know the impacts its having. How do we know it's not natural variation? It all comes back to the timing. Even the fastest spike in pCO2 we can find in the geological record is an order of magnitude slower than the spike we're seeing right now, and that's assuming the fastest possible release at the PETM. If we instead use the 10kyr model, we're two orders of magnitude faster. There is no natural release method of CO2 that acts this fast. While we've been pumping out CO2 since the 1800's, and there is uncertainty on if that early output had a major influence on the environment, by the 1940's we can confidently state that Human activity is the single greatest source of CO2. Raupach et al. (2013) are even able to identify a significant uptick in Anthropogenic output in 2000, coinciding with a marked increase in globalisation activity and a shift toward Coal as a dominant fuel source [8].

Even leaving aside the speed of the rise, the last time we saw pCO2 concentrations of 400 ppm was in the middle of the Miocene, a good 10-14 million years ago (Tripati et. al, 2009) [9]. This is way before the recent Glacial-Interglacial cycle began, and is completely beyond the scope of the natural variations within that cycle.

References:
[1] http://science.sciencemag.org/content/312/5772/428
[2] Link
[3] http://onlinelibrary.wiley.com/doi/10.1029/91JB01898/full
[4] http://www.sciencedirect.com/science/article/pii/S0012821X12000246
[5] http://www.sciencedirect.com/science/article/pii/0195667185900485
[6] http://www.nature.com/ngeo/journal/v3/n3/full/ngeo755.html
[7] http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.260.1482
[8] http://www.nature.com/nclimate/journal/v3/n7/full/nclimate1910.html
[9] http://science.sciencemag.org/content/326/5958/1394

 

and that's a far better answer than the Tom Cruise wannabe gave. which was my point. HE didn't answer the question. So why did you point us to it?

 

Before I answer, it's worth noting that I had the time to compose that post and find the sources over the course of an hour and a half, give or take. If I were put on the spot in the same position as Dr. Cox, I doubt I'd be able to produce nearly as coherent an argument, particularly within the 5 minutes or so he was allotted to respond. Also, it's my area of expertise, it's tangential to his.

For why I linked it, I found the show to be entertaining. The anti-science guy exhibited cartoonish levels of contrarianism, going so far as to contradict everything he could by claiming there was no evidence being shown, whilst producing no evidence of his own to support his attempts to overturn scientific consensus. The one that really just got me was the exchange of '97% of Climate Scientists agree on this' 'Actually, you're wrong, that figure is 0.3%'

To make such a stupendous counter-claim with no backing at all is laughable, and I just wanted to share my amusement.

 

Fair enough. you enjoy vague answers given by someone you agree with. I have no problem with that. And thank you for agreeing with me that his answer was vague.

 

It basically comes down to familiarity with the material. He's totally right about the scale of agreement in the community, as well as the dominant factors that are examined, as is the Mathematician, but because neither of them are active in the research part of the field, they won't naturally know what the specifics are off the top of their head. Give them time to do a little reading, and I'm sure they'll be able to produce a similar response to my own, though perhaps with fewer recent sources.

Incidentally, my enjoyment was primarily from amusement at Anti-Science guy. I don't need to be told what current scientific views are on Climate Change, as I said, I'm actively researching in the area. I initially found a highly edited version of the video showing some of Anti-Science guy's more outrageous claims, saw that Brian Cox was in it too, and figured I should try and find the whole thing. The video I linked is the first one I found that did show the whole show, I imagine the title may be what's leading you to think I watched it to enjoy Brian Cox's comments, but it's literally just the title of the first video I found.

 

you posted a video and said look 11 mins in. I looked 11 mins in. a woman asked for proof that humans contribute to climate change. she wasn't answered. so I asked why you posted this. you answered and im satisfied with your answer. thank you.

 

The time stamp was actually grabbed from another comment, I didn't take the time to double check it myself, but I did know the first question asked was about domestic affairs

 

ahhhh, ok. gotcha.

 

If people put the same effort into curing disease as Comissar puts into his posts we'd have a huge problem with food availability.

 

While I appreciate the sentiment, I think doctoring is a lot harder than putting these posts together

I think that's what Brian Cox is getting at when he says there isn't the political will to see real change right now. And I'm afraid I do agree with him. The situation is one that worries me far more than anything else going on right now, as it is in the most literal sense a global issue. It has to be kept in the forefronts of peoples attention, but doing so inevitably draws out those who would much rather dismiss the evidence and continue as is.

 

Fun fact, I'm now actually using my long post as a place to refer to when I forget what a given reference is for certain things. It's quicker to find than digging through my various word documents.

 

I have no idea how sane people don't actually believe in the human element in climate change.

Almost as bad as nit believing in evolution.

Just... Wow.

 

Oh, and who is that minister? Seems well spoken, I like how he handled this situation.

 

Unfortunately, I don't know Australian politics. Brian Cox and the host are the only familiar faces, and the host only because I've watched a previous Q&A a while ago.

 

Actually I take that back my comment about evolution. The reason this gets me so angry is because of how selfish it is - people are willing to sacrifice the world (although they will never see any of the consequences) for pride. We really need to get moving about climate change.

Arghhhhh this really makes me mad.

 

Agreed on the comparison to Evolution. While anti-evolution folk get me thoroughly irate, it's significantly less harmful than anti-anthropogenic climate change. At least for the former you're "only" harming the education system (don't get me wrong, I'm not trivialising harm to education here). The latter has actively detrimental impacts on the very ecology of the planet, and is highly likely to cause serious destabilisation of our way of living. In comparison, a generation with a shortage of scientists is nothing.