The Moon

Moon2I’m not yet back from my meeting, but I thought I would post this picture of the Moon that I took last night. It’s not quite as sharp as I would like, but you can at least see the structure along the terminator.

I haven’t really been following much of what’s been going on in the climate blogosphere, so I don’t know if I’ve missed anything exciting. I did notice Tamino’s post about the analysis of extremes and his post about Judith Curry’s response. This all seems rather bizarre. How can the mean and standard deviation increase without an increase in the probability of hot extremes? To be honest, I’ve actually really enjoyed being somewhat out of touch, and so plan to do so much more often. Now I plan to go and pack.

Posted in Climate change, ClimateBall, Judith Curry, Science | Tagged , , , , , | 12 Comments

A short break

GTC_presunsetI’m off to a conference tomorrow, and probably won’t be blogging much, if at all (although, I have said that before). I am partly running out of things to say, and also think I need a bit of a break. It does get somewhat wearing after a while, and I think I do need to try and reset my cynicism level. It’ll probably shoot right back up again, but a period of modest optimism would be nice – even if it doesn’t last long. Anyway, I plan to enjoy myself while I’m away (as well as give a talk at the conference, chair a session, and – of course – listen to all of the other talks).

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My issue with Ecomodernism

I was thinking a little more about why I haven’t embraced the ideas behind the Ecomodernism Manifesto. It’s a positive message, and it’s promoting innovation and technology development; all things that I would regard as crucial parts of what we should be doing to address the risks associated with climate change. So, why haven’t I simply accepted that this is the way forward?

One reason is simply the tone. It’s a bit antagonistic and rather dismissive of other ideas. That’s fine, but it doesn’t really give the impression that those involved are actually interested in a genuine discussion. Putting that to one side, though, there is – in my view – a more fundamental issue. I get a bit of flack if I don’t properly recognise that ultimately we should be aiming to balance the risks associated with climate change with the risks associated with the various future pathways. It’s clearly not easy, but I do agree that this is what we should be aiming to do, even if we can’t do it in some kind of exact way. I don’t, however, see much evidence for anything like this in the Ecomodernist Manifesto. It really just seems to be a description of their preferred future pathway (be positive, innovation, technology).

To be fair, they do acknowledge the risks associated with climate change, but then seem to effectively ignore them. For example, a number of those associated with Ecomodernism seem to be promoting the view that we cannot achieve a 2oC limit, that we should therefore accept this, and – given this – simply do the best we can; the “good Anthropocene”. The problem is that the 2oC limit is not some kind of boundary; there’s a continuum. Whether or not having such a limit was a good idea, it was simply intended as a target, rather than as some kind of divider between “good” and “bad”. Even if we are going to miss this target, there is still a vast difference between missing it by a lot and missing it by a little.

So, the impression I have is that part of the justification for the Ecomodernist idea is that because we’re going to miss this target, we should now ignore targets, and simply focus on how best to develop technologies for the future (a variant of the “no regrets” idea, I think). In a sense, ignore the risks associated with climate change because we can’t avoid them, and focus – instead – on technology that will let us deal with this. Of course, I agree with the general idea of technology development, but how much we priortise this, how we do it, what we actually focus on, and how quickly we change our energy sources is still relevant. Broadly speaking, how much we warm will depend only on how much we emit. The more we emit, the more we will warm and the more likely it will be that the impacts of climate change will be more severe. Implying that it’s somehow binary (we’re going to miss the target, move on) seems to ignore that it’s still likely to be better to miss it by 0.5oC than to miss it by 1.5oC.

To be fair, this idea seems quite new and maybe there is more to it than I appreciate. If anyone knows of any other documentation that explains it in more detail, feel free to point that out. Similarly, if anyone wants to explain it in more detail in the comments, go ahead. However, while it appears to be more a mechanism for justifying a preferred pathway, than something based on a genuine analysis of the various risks, I suspect it will remain something that is largely accepted by those who find these ideas particularly appealing.

Posted in Climate change, Climate sensitivity, ClimateBall, Science | Tagged , , , , , | 274 Comments

Assessing anthropogenic global warming

This post is really a joint post, written by myself and by Roger Pielke Sr. It’s partly a continuation of a post Roger wrote on Judith Curry’s blog, and partly a consequence of my attempt to answer one of Roger’s question. The latter post resulted in a rather tetchy exchange between myself and Roger which we’ve now resolved, illustrating that it is possible to recover from such exchanges (I sometimes wish more would try to do so – sometimes I don’t, though).

This post is really just intended to be a simple illustration of how one might use the forcing/feedback paradigm to both understand and quantify anthropogenic global warming, and – potentially – as a mechanism for assessing global climate models. It is a work in progress, and this is simply a draft. So, bear that in mind. Comments welcome.

The definition of a forcing is essentially the net change in energy balance (change in net TOA flux) due to external (e.g. solar), volcanic emissions and internally human imposed perturbations (e.g. added CO2) . Typically, it has been defined relative to some baseline time period (IPCC, 2013). This change in energy balance will cause warming/cooling and a temperature response, which will then produce a feedback response. If the change in forcing at time t (relative to t = 0 ) is \Delta F(t), and the change in temperature is \Delta T (also relative to t = 0) then the radiative imbalance, N(t), at time t is

N(t) = C \dfrac{d \Delta T(t)}{dt} = N(0) + \Delta F(t) - \lambda \Delta T(t), (1)

where N(0) is the imbalance at t = 0, and \lambda is the feedback response in Wm-2K-1, C is the heat capacity. If we assume that the system is in radiative balance at t = 0, then we have

N(t) = C \dfrac{d \Delta T(t)}{dt} = \Delta F(t) - \lambda \Delta T(t). (2)

It is important to note that the feedbacks are assumed a linear function of \Delta T(t). That this might not be correct is discussed in the post. In addition, there are radiative forcings/feedbacks that are not directly connected to \Delta T(t) as dicussed in NRC (2005), such as from the input of cloud condensation nuclei and ice nuclei and their subsequent effect on clouds.

We can actually put some numbers in. According to the GISS dataset, the change in forcing between 1880 and 2011 is 1.635Wm−2, and the change in temperature is 0.77K. The feedback response (Soden & Held 2006; Wielicki 2013) is about \lambda = 1.21Wm−2K−1. We assume \lambda is positive for a net negative feedback (i.e., minus in Equation (2)). Therefore the radiative imbalance in 2011 should be

N(2011) = \Delta F(2011) - \lambda \Delta T(2011) = 1.635 - 1.21 \times 0.77 = 0.7 {\rm Wm^{-2}}. (3)

If we consider the NOAA Ocean Heat Content data, then it suggests that the oceans are currently accruing energy at the rate of about 1022 J/year. If this is ~93% of the total system heat uptake rate. The radiative imbalance is therefore

N[NOAA(2011)] = \dfrac{10^{22}}{0.93 \times 3.15 \times 10^7 \times 4 \pi 6370000^2} = 0.67{\rm Wm^{-2}}. (4)

We can also estimate how the total system energy changes with time by integrating Equation (2) in time. In other words

{\rm OHC}(t) = \int_0^t N(t) dt = \int_o^t C dT = \int_o^t \left[ \Delta F(t) - \lambda \Delta T(t) \right] dt. (5)

Figure 1: Estimate of the change in Ocean Heat Content (OHC) by integrating a simple energy balance formalism.

Figure 1: Estimate of the change in Ocean Heat Content (OHC) by integrating a simple energy balance formalism.

If we compare the results shown in Figure 1 with the NOAA 0-2000m Global Ocean Heat Content shown in Figure 2, then our results suggest that the system should have accrued about 2 × 1023 J between 1970 and 2011, while the NOAA data suggests about 2.5 × 1023 J over the same period. The NOAA data is also for the oceans only, and so only accounts for about 93% of the change in system energy.

Figure 2: Figure showing the change in 0-2000m and 0-700m Global Ocean Heat Content (OHC) - Levitus et al. (2012).

Figure 2: Figure showing the change in 0-2000m and 0-700m Global Ocean Heat Content (OHC) – Levitus et al. (2012).

With respect to other estimates, The heat content of the world’s oceans for the 0-2000m layer increased by 2.4 x 1023 J corresponding to a rate of 0.39 Wm-2, according to Levitus et al 2012. The layer from the surface to 2000 m depth warming rate of 0.39 Wm-2 ± 0.031 Wm-2 per unit area of the Earth’s surface accounts for approximately 90% of the warming of the climate system according to Levitus et al. Thus, if we add the 10%, the 1955-2010 the radiative imbalance is 0.43 Wm-2 ± 0.031 Wm-2. About 1/3 of this heating is at levels below 700m, according to Levitus et al 2012. They concluded that a strong positive linear trend in exists in world ocean heat content since 1955. Since about 2003, the heating rate in the upper 700m was less than in the earlier years back to around 1997 (Figure 3).

Figure 3: Figure showing the 0-700m change in Global Ocean Heat Content (NOAA).

Figure 3: Figure showing the 0-700m change in Global Ocean Heat Content (NOAA).

The IPCC reports that the global average radiative imbalance is 0.59 Wm-2 for 1971-2010 while for 1993-2010 it is reported as 0.71 Wm-2. Trenberth and Fasullo (2013) state that the imbalance is 0.5–1Wm−2 over the 2000s.

Our basic calculation would seem to be slightly underestimating the change in total energy. This could be due to errors in the forcings, feedbacks, or temperature response. It is possible that we should lag the temperature response slightly to account for the time it takes for the upper ocean to equilibrate with the atmosphere.

There is also the issue of the heating that has been reported below 700m in the oceans. Levitus et al report [and Figure 2 illustrates] that about 1/3 of the heating has gone into that layer. If correct, this heat is not likely to transfer back to the surface so as to affect weather and other aspects of the climate on multi-decadal time scales. Also, if more goes into the deeper parts of the ocean, there is less to heat the surface – slower surface warming. If less goes into the deeper parts of the ocean, then there is more to heat the surface – faster surface warming. This heat is, however, not sampled when a surface temperature trend is used to diagnose global warming.

Levitus S., et al., 2012, World ocean heat content and thermosteric sea level
change (0–2000 m), 1955–2010, Geophysical Research Letters, 36, L10603.

National Research Council, 2005: Radiative forcing of climate change: Expanding the concept and addressing uncertainties. Committee on Radiative Forcing Effects on Climate Change, Climate Research Committee, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, The National Academies Press, Washington, D.C., 208 pp.

Soden B.J., Held I.M., 2006, An Assessment of Climate Feedbacks in Coupled Ocean–Atmosphere Models, Journal of Climate, 19, 3354-3360.

Wielicki B.A., et al., 2013, Achieving Climate Change Absolute Accuracy in Orbit, Bulletin of the American Meteorological Society, 94, 1519-1539

For a bit of fun, I coded up the simple two-degree-of-freedom model that Isaac Held discusses here. The basic model is meant to represent a mixed layer with a temperature T and heat capacity C, and the deeper ocean with temperature T_o and heat capacity C_o. The basic equations are

C \dfrac{dT}{dt} = -\beta T - \gamma (T - T_o) + F(t)

C_o \dfrac{dT_o}{dt} = \gamma (T - T_o).

In this case I integrated the equations for T and T_o using the forcing timeseries. I used \beta = 1.5 and \gamma = 0.5, which gives an ECS of 3.7/\beta = 2.5^o{\rm C} and a TCR to ECS ratio of \beta / (\beta + \gamma) = 0.75, giving a TCR of 1.9^o{\rm C}. You can get the change in OHC using the change in temperatures and the heat contents of the two layers. The basic result is shown in the Figure below. The upper figure shows the temperature compared to GISSTemp (dashed line), the lower shows the OHC since 1950. I did this really quickly and am not trying to match anything exactly. This is just meant to be illustrative, so bear that in mind.



Posted in Climate change, Climate sensitivity, Science | Tagged , , , , , , | 125 Comments

The allure of articulate confidence.

I watched BBC One’s Saturday Morning Live, which included James Delingpole discussing the Pope’s Encyclical Letter. I think you can watch the episode here. What it seemed to illustrate, to me, was both the allure of articulate confidence and why you don’t debate science.

Delingpole was certain that climate change has played no role in the recent migrant crisis. I don’t know if it has, but I also don’t know if it hasn’t. He’s certain that climate change is simply a natural process; not partly natural, just natural. Typically scientists are not nearly as certain about such topics as Delingpole appears to be. That’s why debating science is not the norm. If your goal is to gain some understanding, how can you do so if one party is willing to make confident assertions? Especially, if this – as is the case with Delingpole – is coming from a position of obvious ignorance.

Of course, one positive to take from this is that if Delingpole is the best that the BBC can get, they really are scraping the bottom of the barrel. One suggestion I would make is that the BBC aim to ensure that those who they invite to talk about a complex topic, like climate science, at least have a modicum of actual expertise in that subject. If they did so, that would immediately eliminate the likes of Delingpole. Of course, it might make such segments less interesting, but I’d certainly favour being informative over being controversial.

This is probably an opportune time to include, again, the discussion between James Delingpole and Paul Nurse, in which Delingpole illustrated that he really isn’t a scientist, and doesn’t have a particularly good understanding of science, or the scientific method.

Posted in Climate change, ClimateBall, Satire, Science | Tagged , , , , , , | 87 Comments

My best photograph

CrevasseSince I’ve been posting some photographs, I thought I would post what I regard as one of my best photographs. I have no idea if it is objectively a good photograph, but I really like it. It’s also one of the few photographs I’ve ever had published – in a magazine that went bust shortly afterwards. The photograph was taken in a crevasse in the Antarctic in late 1992, or early 1993 (I think), and the person in the photograph was one of our medics. Technically, we weren’t really meant to go down crevasses, but that didn’t really stop us and I don’t really remember being told explicitly that we shouldn’t. It’s also hard not to, when you have the chance to actually do so.

In_crevasseSometimes, the opportunity was also just too good to pass up. There was a lot material being transported to a new site, for building a new base. We’d hired some ex-Russian missile carriers to speed things up, as they were much faster than the vehicles we had. In this case, the South African co-driver and the Russian driver had, I believe, shared more of a bottle of vodka than was wise and had decided that a short-cut was in order. The photograph to the left shows what can happen when you go off route in the Antarctic. Since the crevasse was now open, we took the opportunity to explore – ostensibly to check what was underneath the vehicle, but really just to have a look around.

YellowHutFortunately, it was good weather and close to the site of the new base, so noone was hurt, and the recovery was fairly straightforward. Once it had been pulled out, one of our mechanics welded it all back together again. It also turned out that the hut that I was using for all of my experiments (and in which I used to sleep) was almost the same colour as the vehicle. So, we found some old paint, covered up all the welds, and everyone got back to work. On that note, I must go and make a curry for dinner.

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Climate Wars Bingo

Matt Ridley has a recent article in Quadrant Magazine called The Climate Wars’s Damage to Science. Interestingly, he doesn’t appear to discuss his own role. I have no great interest in discussing the article in depth. My main suggestion to Matt would be that he consider that the bad ideas [that] can persist in science for decades, are simply ideas he doesn’t understand. What really struck me, though, was that it would be fantastic article for playing something like Climate Wars Bingo. I’d only read the first few paragraphs before encountering a discussion of Lysenkoism. There’s the obligatory mention of Green funding. There’s Greenpeace. There’s alarmism. I haven’t waded my way through the whole article, but it seems to cover all possible bases. Is anything missing?

Posted in Climate change, ClimateBall, Comedy, Satire | Tagged , , , , , | 93 Comments