Highlighted Enquiries

Response

Yes, man-made climate change is increasing the probability of floods such as that experienced in Thailand.

According to IPCC (2007):

Globally, the number of great inland flood catastrophes during 1996–2005 was twice as large, per decade, as between 1950 and 1980, while related economic losses increased by a factor of five. Socio-economic factors such as economic growth, increases in population and in the wealth concentrated in vulnerable areas, and land-use change were significant contributors. Floods have been the most reported natural disaster events in many regions, affecting 140 million people per year on average. In Bangladesh, during the 1998 flood, about 70% of the country’s area was inundated (compared to an average value of 20–25%). Because flood damages have grown more rapidly than population or economic growth, other factors must be considered, including climate change. The weight of observational evidence indicates an ongoing acceleration of the water cycle. The frequency of heavy precipitation events has increased, consistent with both warming and observed increases in atmospheric water vapor.

Min, et al. (2011) investigated heavy precipitation events in the United States between 1951 and 1999 and found:

Human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events found over approximately two-thirds of data-covered parts of Northern Hemisphere land areas. Changes in extreme precipitation projected by models, and thus the impacts of future changes in extreme precipitation, may be underestimated because models seem to underestimate the observed increase in heavy precipitation with warming.

Pall, et al. (2011) analyzed the United Kingdom floods of autumn 2000 - the wettest autumn in England and Wales since records began in 1766. Their analysis showed:

...that it is very likely that global anthropogenic greenhouse gas emissions substantially increased the risk of flood occurrence in England and Wales in autumn 2000...The precise magnitude of the anthropogenic contribution remains uncertain, but in nine out of ten cases our model results indicate that twentieth century anthropogenic greenhouse gas emissions increased the risk of floods occurring in England and Wales in autumn 2000 by more than 20%, and in two out of three cases by more than 90%.

2010 was the wettest year on record for the globe and 2011 was second.

Response

Two Responses:

1)

In regards to the latter question first, the series for each of the three major datasets is freely available online for anyone to access and analyze as they see fit.
http://www.metoffice.gov.uk/hadobs/hadcrut3/diagnostics/global/nh+sh/
ftp://ftp.ncdc.noaa.gov/pub/data/mlost/operational/products/ (you'd need the readme file and either monthly or annual land+ocean90N90S)
http://data.giss.nasa.gov/gistemp/tabledata_v3/GLB.Ts+dSST.txt


Some basic points on the first question:
1. Single years are not climatically indicative. If you look at http://www.ncdc.noaa.gov/sotc/global/ and more specifically http://www1.ncdc.noaa.gov/pub/data/cmb/hazards/2011/12/enso-global-temp-anomalies.png you can see that the state of ENSO makes a very substantial difference to annual values. La Nina years are generally depressed by of the order 0.1-0.2C and El Nino enhanced by a similar magnitude. Starting your series in 1998 - the strongest El Nino we have seen in recent decades - yields a significantly warm-biased start point. If I calculated a trend starting just two years earlier (a strong la Nina) I would conclude that the climate is warming very fast indeed. Neither makes any scientific sense. There is a reason why WMO defines climatological normals as 30 year averages and its scientific rather than dogmatic.


2. Various analyses have been undertaken looking at how often in climate simulations, even with strong background forcing of the model by greenhouse gases etc., such apparent hiatuses over short periods occur. These analyses have consistently implied that somewhere in the range of 15-20 years of apparent hiatus in warming is possible even under a strong external warming influence. This is because the real climate system (and the simulated climate system) are the sum of forcing response and internal climate variability. Internal climate variability over periods of a decade or two is capable of both masking and enhancing the long-term forced response component. This is why we need to look at the long-term because it is on the long-term that natural variability averages out towards zero and the forced response component becomes the dominant factor determining trends. Bottom line: Even without invoking additional factors to natural variability the recent temperature evolution is entirely consistent with increasing greenhouse gas loadings.


3. There is strong and compelling evidence that HadCRUT3's best-guess global value has under-estimated the trend since the late 1990s. There are two reasons. First, over land the dataset has, by chance, tended to sample areas showing less warming than the global mean. This is the largest impact. Its effect is documented in the recent CRUTEM4 paper that has just appeared at JGR and which concludes that the land aspect warming has been under-estimated in HadCRUT3. Second, the ocean measures have seen a change from predominantly ship-based measures to predominantly buoy based measures. Ships are warm-biased compared to buoys, so in HadCRUT3 which made no adjustments, the net effect is an artificial cooling bias. This has been accounted for in the latest Hadley Centre SST product. When these are combined to form the new HadCRUT dataset I fully expect that dataset to exhibit a greater recent warming than HadCRUT3 does.

As stated above my view is that the short period trend analyses are of relatively little value scientifically. The changes seen on longer timescales are more important as on the longer timescales the response to external forcing dominates over natural climate variations. More important still than that is that we are seeing changes in a plethora of climatic variables which we would expect to be changing if the world were indeed warming. Both the troposphere and the sub-surface ocean are warming. Surface and tropospheric humidity are increasing. Arctic summer sea-ice is retreating. Spring snow melt comes earlier. Glaciers have receded on a global average basis every year for more than two deacdes and the rate of loss is accelerating. Sea level is rising. The surface temperature record is but one sub-set of the big picture. Even if we had never invented the thermometer we would still be concluding that the climate is changing. The evidence abounds from the top of the atmosphere to the depths of the oceans. It does not depend on any single indicator or single dataset. Mother nature is not swayed by opinions or arguments no matter how coherent and compelling they may seem to us and she is shouting loud and clear that she is changing and that the world is warming.
http://www.ncdc.noaa.gov/bams-state-of-the-climate/2009-time-series/ - gives more info on this and some interactive tools. The series are a little dated now (2 years)

I am not a solar physicist but it is beyond any reasonable doubt that this current solar cycle has been unusual at least in the context of those observed in the (very short) instrumental record. But there is a danger in obsessing over single forcing mechanisms. In reality there are many factors in play that are influencing our climate: greenhouse gases, aerosols, volcanoes, solar changes, land use/land cover change etc.. There has been a lot of recent work looking at the influence of stratospheric water vapor loadings and the large number of relatively small volcanoes that have gone off in the last decade. There is increasing evidence in the literature that both of these, for example, may have imparted a cooling influence much larger than the recent solar cycle. Its important to recognize just how complicated a beast the climate system and its myriad influences truly are, particularly when explaining short-term behavior.

2)

Your e-mail was forwarded to me, and I'm happy to respond to your question. I have great understanding for your concerns, and I realise how confused people may be about these issues, especially after the op-ed in the Wall Street Journal (WsJ) signed by 16 scientists. I will explain why I think that the claims in the MoS article and WsJ op-ed are incorrect, but first I'd like to draw your attention to the fact that there is a response to this op-ed in Today's WsJ,
http://online.wsj.com/public/page/letters.html

also on:

http://climatecommunication.org/news/setting-the-record-straight-on-climate-change-experts-respond/

The original WsJ article was written by scientists who had little work experience in climate science, whereas the response - to which admittedly I contributed - was signed by 38 climate scientists. Basically, we support the view of the UK Met Office.

There is a recent study published in the scientific journal Environmental Research Letters (ERL) - for which I wrote a perspective - see http://stacks.iop.org/1748-9326/7/011002 - that explains why we see jumps and dips in the temperature record. Once known natural phenomena are accounted for, one is left with a fairly straight line showing a remarkably constant warming.

Furthermore, the MoS and WsJ articles only refer to one set of analyses (HadCrut3), which I find a little dishonest - There are several analyses, and the one to which they refer to is the data set that shows the *least* warming rate in the last 10-15 years. The reason for this is that there are few measurements in the Arctic region where the recent warming has been pronounced (also seen in the sea-ice retreat, melting ice on Greenland, and record-high temperatures on Svalbard). The different data sets use different strategies for dealing with this data void, and the strategy chosen by the HadCrut3 ignores this rapid warming region and hence places the least weight on it.

The irony is that there is a brand new version of the analysis from CRU: CRUTEM4 - the scientific paper is still in press, but you can read the abstract at http://www.agu.org/pubs/crossref/pip/2011JD017139.shtml.

Furthermore, there are plenty of other independent climate indicators all pointing to a continued warming:
http://www.ukcip.org.uk/essentials/climate-indicators/

I find it a bit odd that scholars can dismiss the global warming on the basis of one selective choice of data and ignore all the other evidence. Such practice I hope would never hold up in a court.

Response

Two Responses:

1)

1) There is large natural variability, led by ENSO and also the North Atlantic Oscillation, which is related to what is sometimes called the Northern Annular Mode (NAM) and the Arctic Oscillation (AO). The latter are the same (I don't like the term AO as it is neither Arctic nor an Oscillation). The NAO is a more regional version of the NAM. Given any natural variability, its manifestations in terms of temperatures and precipitation are apt to be changed by global warming from human influences. Temperatures are, on average, a bit higher and heat waves can become very pronounced owing to feedback effects. Higher temperatures, and especially sea temperatures, mean that the water holding capacity of the atmosphere is greater, and so it tends to produce more intense precipitation events: both rain and snow. Whether it is snow depends on temperature. So droughts are more intense and last longer, and there is greater risk of flooding. Where these occur is determined by these patterns, most of which is "natural".

2) A key question is why has the NAM/NAO been so extreme in the past few years and of opposite sign. It is a good scientific question. Firstly, we know that these phenomena occur naturally in models, even in atmospheric models (without the ocean) and so it is largely a natural mode of variability in the atmosphere. In the southern hemisphere there is a related mode called the Southern Annular Mode (SAM). In the Northern Hemisphere the land/sea distribution focuses the action more into the North Atlantic, hence the NAO. Secondly, just because it is a natural mode, does not mean it isn't affected by other things.

3) So what things might change the NAM/NAO? We know the SAM has increased in the positive phase over time so the polar vortex in the SH is stronger. This is mainly because of the ozone hole. However increased carbon dioxide works in the same direction by cooling the stratosphere. The stratospheric influences are clearly important. Also, the strength of the overall westerlies in both hemispheres is related to equator to pole temperature gradients. These are affected by climate change but in complex ways. Obviously at the surface, Arctic sea ice loss reduced the polar temperatures and acts to make the NAM negative perhaps. Warming in the tropics though, increases with height and increases the NAM/NAO. Both effects are playing a role but are not sorted out adequately. In the stratosphere, several things come into play. One is clearly ozone and it was reported last year that an ozone hole had developed in the NH. This varies a lot from year to year but it is apt to play a role in the NAM/NAO variations. In the tropics there is a stratospheric phenomenon called the QBO: the Quasi biennial Oscillation, that has an average period of about 28 months. It is a natural variation that is reasonably understood. It can influence the higher latitudes and may have some influence on the year to year variability in NAM/NAO. Another factor that has been identified is the role of the sun, which has greatly amplified variations in the Ultraviolet (UV) with the sunspot cycle that in turn affects ozone. The sun went through a very quiet phase but this year has bounced back as part of the 11 year sunspot cycle and is now at above average activity. There is a paper on this aspect (I think it is not proven), but it clearly identifies a role for the solar variability in the stratosphere and it affects the NAM/NAO.

4) So there are a number of factors that may be playing a role, but the understanding is incomplete and we do not have a definitive answer for you. My best guess is that the stratospheric variations, which are influenced by the solar activity, the QBO and ENSO, will help explain not only the variations but also their extreme nature in what is otherwise a natural variability. Here is the sun variability.

Certainly the dominant external influence on the atmosphere has been the La Nina, and it has had a profound effect across North America via the wave train generated, that alters the jet stream and associated storm tracks. The main anomalies in precipitation and atmospheric heating are in the Pacific.

This La Nina is very different from a year ago mainly because it is not on the heels of an El Nino. The very high SSTs in other oceans are largely missing this year, so the action is more focussed in the Pacific, not the Atlantic or Indian oceans. The La Nina is moderate but always these days the manifestations are increased (enhanced) in terms of precip and T anomalies owing to global warming aspects.


2)

"Climate change can impact some weather patterns more than others. What we expect to see is the following:

1. Redistribution of water. As a general rule of thumb, we expect areas that are currently wet to become wetter and areas that are currently dry to become drier. In the US, we expect the Western 1/3 of the country to become drier and the Eastern 2/3 to become wetter. Guess what, we are seeing just that trend.
2. We expect to see precipation come in heavier and heavier doses. So, when it rain (or snows), it will really pore.
3. We expect to see extremes become more extreme and last longer.
4. Heat waves are more likely and will be more severe. There is evidence that a significant portion of the 2010 Russian heat wave was attributed to climate change.

It is more difficult to make conclusions about things like hurricanes and much more difficult to make conclusions on tornadoes.

If I were to summarize in a sentence, it is this: ALL THE WEATHER WE ARE SEEING NOW IS BEING AFFECTED BY CLIMATE CHANGE"

Response

My best guess looking at the blogs you mention is that the basis for that accusation is that we used NOAA/NCDC’s GHCN (global historical climate network) data as our only source for the US up to 1999, then – in year 2000 - replaced the US data by the adjusted USHCN data. These adjustments (made by the NOAA/NCDC group, not by NASA/GISS) corrected for well-researched biases produced by documented station moves and documented changes in the measuring protocols. The effect of this source switch on global temperatures was statistically insignificant, however the US mean temperature series was affected substantially.



NOAA/NCDC recently redesigned the web documentation of their work, giving more emphasis on a newer procedure to adjust the data. In particular a nice graph that showed the effect of each adjustment on the US temperature series is no longer part of that display. But you still can find the corresponding graphs in our paper


http://pubs.giss.nasa.gov/docs/2001/2001_Hansen_etal.pdf



Look at the graphs (B) on page 18 and you’ll see that most of the tilting is produced by the Time-of-Observation debiasing and by the station history adjustments; both biases seem to have hidden some of the warming that occurred. NOAA/NCDC’s USHCN data are still available, both the unadjusted and the various adjusted versions and those graphs can easily be checked.



In summary: “NASA/GISS tweaking” is really “NOAA/NCDC’s correcting of artificial biases based on careful studies of the available meta data”.

Response

Two responses:

I)

1)*The section below says that there's no scientific literature that offers guidance on impacts of incremental GHG pollution. Doesn't social cost of carbon research satisfy that condition? Is there other literature that policy makers could use? Are the other claims made about
the scientific literature fully accurate?*

The statements made in this section of the Alton Coal Tract Deaft EIS (Alton DEIS in the following) are mostly factually correct, but certainly tend to mislead the reader in implying that no assessment of the climate impact can be made. It is correct that no scientific tools exist to assess the relationship between emissions of greenhouse gases (GHGs) from a specific single
source and its localized impacts. The reason for the lack of such studies is simply that it makes scientifically no sense to try and link specific emissions to local impacts. This is because, as correctly mentioned in the section, GHGs emitted from a given source are quickly mixed into the global atmosphere and thus have an impact primarily on the global scale. Simply put, on any time scale longer than a few days, it is impossible to link the carbon dioxide (CO2) molecules in the air over Utah to the CO2 sources in that state. Thus, the CO2-related climate change that will affect Utah is not directly caused by the local
emissions, rather it will be caused by the aggregate global CO2 emissions. It is also true that regional climate projections are less certain than projections for the global mean. Regional climate models are always embedded in global analyses, so they cannot be better than the global
models and introduce additional uncertainties through their necessarily simplified representation of local scale features.

While these points are correct, I would dispute the conclusion that no assessment of the climatic impact of specific activities associated with GHG emissions is possible. The correct metric to assess the climate
impact of any GHG emissions is the fraction of these emissions compared to the total projected global emissions, which then can be related to the expected global (and regional, if suitable projections exist)
climate impacts of the respective rise in GHG concentrations of the atmosphere.

Performing such a calculation in detail is complicated, but simple order-of-magnitude estimates are certainly possible. The basic data for such estimations are provided by the IPCC reports. In the following I perform an estimation from numbers that I have in mind, it should be regarded as a rough estimate only. IPCC states that global climate will warm by 3 °C (2 to 4.5°) if CO2 is doubled from its pre-industrial level of 280 ppm to 560 ppm. Presently, about 8 GtC (Gigatons of Carbon) are
emitted annually, leading to an increase of CO2 concentrations in the atmosphere of about 2 ppm/yr. Thus, 140 years of such emissions are needed to double CO2, or 140 x 8 = 1120 GtC cumulated emissions. Now,
the CO2 emissions expected from burning the coal to be extracted from the Alton coal mine could be related to this estimate of roughly 1000 GtC that will lead to 3 °C global warming (and the related regional impacts, if a respective assessment exists). Whatever the amount of coal in the Alton mine may be, the number in terms of warming that results from such an estimation will be very small, such that one might be tempted to say that the impact of these specific emissions is negligible. While this is correct, it is a fact that the global GHG increase and related climate change results from the sum of a myriad of GHG sources, each of which on its own may be called negligible. For this reason, the calculation of a specific climate impact (contribution to global/regional warming, or any other quantifyable impact such as sea-level rise, etc.) of a specific GHG source is not very informative. If I were to write an EIS for such a source, I would rather relate the expected emissions to the total emissions in the respective state or country and the policy goals for such emissions that may exist there. For example, if Utah (or the US) had any specific emission targets (such as provided e.g. by the Kyoto protocol), it would be a relevant question to ask how strongly the emissions from the Alton coal mine would affect the achievement of these goals, or how these emissions could be compensated for by other measures.

You are very right about mentioning the social cost of climate change as offering guidance on impacts of incremental GHG pollution. One may refer to the famous Stern report to estimate these costs (N. Stern, The
Economics of Climate Change: The Stern Review, Cambridge Univ. Press, Cambridge, 2006). One could estimate the fractional cost of the emissions of a give source along the lines sketched above. In fact, this
has been done in the Stern review, where the social cost of of carbon is estimated to lie between $25 and $30 per ton of CO2 (see chapter 13 of the review and Stern and Taylor, 2007, Science 317: 203-204). Such a number may provide the simplest way of estimating the overall impact of any specific CO2 source.


2)***Is this portrayal of climate change a fair summary of the state of climate science? Is the level of uncertainty about anthropogenic influence implied by "possible" and "potential" and "may" reasonable?*

The language used in this section is clearly very cautious and understates the level of certainty that has been reached by now. I recommend to take the wording of the IPCC reports as guidance in this respect, as is represents the scientific consensus and in particular
because the levels of certainty of the statements made in these reports is very clearly defined.

In the following I cite statements from the Summary for Policymakers of the 4th IPCC report (IPCC, 2007, Climate Change 2007: The Physical Science Basis, available at http://www.ipcc.ch) in comparison to the
statments in the Alton DEIS. The comparison shows that the level of certainty that the IPCC has agreed upon is clearly higher than that implied by the Alton assessment.

Alton DEIS:
GHGs have been identified as a *possible* contributor to the rise in global mean temperatures.
[...]
The study of global climate change is complex because there are many factors that *may contribute* to changes in the earth‘s temperature, including the emission of GHGs [...].

IPCC SPM:
Most of the observed increase in globally averaged temperatures since the mid-20th century is *very likely* due to the observed increase in anthropogenic greenhouse gas concentrations. [remark: Very likely is defined as a bigger then 90 % probability of
occurrence]


Alton DEIS:
Through complex interactions on a regional and global scale, these changes *are thought to* cause a net warming effect of the atmosphere [...].

IPCC SPM:
The understanding of anthropogenic warming and cooling influences on climate has improved since the Third Assessment Report (TAR), leading to *very high confidence* that the globally averaged net effect of human activities since 1750 has been one of warming [...].
[remark: Very high confidence is defined as a 90 % certainty, i.e. a 9 out of 10 chance of being correct]


Alton DEIS:
Ongoing scientific research has identified the *potential impacts* of anthropogenic (from human activities) GHG emissions and changes in biologic carbon sequestration on the global climate.

IPCC SPM:
At continental, regional, and ocean basin scales, numerous long-term changes in climate have been observed. These include changes in Arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones.
[remark: These changes are unequivocally observed and thus portrayed as facts. Their attribution to anthropogenic climate change is very likely, as the past warming is attributed to the GHG increase, as stated above].

II)

This is a response to your query to CSRRT. For completeness, the questions refer to an environmental impact analysis by the Bureau of Land Management of the expansion of a coal strip mine in Utah, at
http://www.blm.gov/pgdata/etc/medialib/blm/ut/lands_and_minerals/coal/alton_coal_project.Par.62082.File.dat/8__Alton%20DEIS%20Chapter%203.pdf


Q1. The section below says that there's no scientific literature that offers guidance on impacts of incremental GHG pollution. Doesn't social cost of carbon research satisfy that condition? Is there other literature that policy makers could use? Are the other claims made about the scientific literature fully accurate?

This question refers to a section of the report (quoted below) in which the central claim is "The climate change research community has not yet developed specific tools for evaluating or quantifying end-point impacts attributable to the emissions of GHGs from a single source".

This claim misses the implication of the fact that impacts of long-lived GHGs (CO2, methane etc) occur over time scales of decades or longer, and at global spatial scales because the atmosphere is well mixed over timescales longer than a year or two. Therefore, the reason that "the climate research community has not developed tools for quantfying end-point impacts attributable to emissions from a single source" is NOT that the problem is difficult or intractable; rather it is that the problem is irrelevant, because single-source impacts are globally shared. There is a lot of work on short-range dispersion of pollutants for air quality applications which could (in principle) be adapted to short-range dispersion of long-lived GHGs, but the result would be a tiny contribution to the well-mixed global background.

This fact is often misconstrued as implying that GHG emissions from any specific source or even any specific small country are irrelevant ("Australia emits only 1.3% of global emissions, so individual action by Australia cannot fix climate change, so Australia should take no individual action"). It is possible that the proponents of the Utah coal strip mine are making this argument. The problem is that the argument leads directly to a tragedy-of-the-commons outcome (Hardin G (1968) Tragedy of Commons. Science 162:1243) in which nobody takes any action and climate change is locked in. The reference in the question to "social costs of carbon research" is therefore heading in exactly the right direction.

Other possible sources for policymakers include the modern literature on solutions to tragedy-of-the-commons problems in environmental management; see for instance
Dietz T, Ostrom E, Stern PC (2003) The struggle to govern the commons. Science 302:1907-1912.
Pretty J (2003) Social capital and the collective management of resources. Science 302:1912-1914

and there is a great deal more. However, one implication of this literature is the need for social capital and institutions for governance of commons. The necessary social capital and institutions at global scale are still highly embroynic, as evidenced by the continued flourishing of the argument "my contribution is small and therefore doesn't matter". (Try that on as an argument for paying no tax ...).


Q2. Is this portrayal of climate change a fair summary of the state of climate science? Is the level of uncertainty about anthropogenic influence implied by "possible" and "potential" and "may" reasonable?

The qualifiers ("possible", "potential", "may") completely understate the confidence of the scientific community in the broad conclusions of climate science and the consequent imperative for action to reduce emissions. The conclusions of the IPCC (2007) Fourth Assessment were essentially that warming is unequivocal and attribution to human influence can be made with very high confidence. Numerous national scientific academies and peak bodies have released their own assessments over the last few years, reinforcing this position. To quote one example with which I was involved personally, the Australian Academy of Science in 2010 released "The Science of Climate Change: Questions and Answers" (http://www.science.org.au/reports/climatechange2010.pdf) which begins by saying
The Earth’s climate has changed. The global average surface temperature has increased over the last century and many other associated changes have been observed. The available evidence implies that greenhouse gas emissions from human activities are the main cause. It is expected that, if greenhouse gas emissions continue at business-as-usual rates, global temperatures will further increase significantly over the coming century and beyond. The science behind these statements is supported by extensive studies based on four main lines of evidence: ... [physical principles, the record from the distant past, measurements from the recent past, climate models].

Hence the qualifiers in the question are far from an accurate reflection of the state of climate science.