Posts Tagged ‘climate change’
After promising to have our flagship paper on reconciling the signal and noise of global warming on decadal timescales subject to open review, it is finally on. The paper has been submitted and accepted for open review at Earth System Dynamics.
Reconciling the signal and noise of atmospheric warming on decadal timescales
Roger N. Jones and James H. Ricketts
Victoria Institute of Strategic Economic Studies, Victoria University, Melbourne, Victoria 8001, Australia
Received: 13 Aug 2016 – Accepted: 22 Aug 2016 – Published: 23 Aug 2016
Interactions between externally-forced and internally-generated climate variations on decadal timescales is a major determinant of changing climate risk. Severe testing is applied to observed global and regional surface and satellite temperatures and modelled surface temperatures to determine whether these interactions are independent, as in the traditional signal-to-noise model, or whether they interact, resulting in steplike warming. The multi-step bivariate test is used to detect step changes in temperature data. The resulting data are then subject to six tests designed to show strong differences between the two statistical hypotheses, hstep and htrend: (1) Since the mid-20th century, most of the observed warming has taken place in four events: in 1979/80 and 1997/98 at the global scale, 1988/89 in the northern hemisphere and 1968/70 in the southern hemisphere. Temperature is more steplike than trend-like on a regional basis. Satellite temperature is more steplike than surface temperature. Warming from internal trends is less than 40 % of the total for four of five global records tested (1880–2013/14). (2) Correlations between step-change frequency in models and observations (1880–2005), are 0.32 (CMIP3) and 0.34 (CMIP5). For the period 1950–2005, grouping selected events (1963/64, 1968–70, 1976/77, 1979/80, 1987/88 and 1996–98), correlation increases to 0.78. (3) Steps and shifts (steps minus internal trends) from a 107-member climate model ensemble 2006–2095 explain total warming and equilibrium climate sensitivity better than internal trends. (4) In three regions tested, the change between stationary and non-stationary temperatures is steplike and attributable to external forcing. (5) Steplike changes are also present in tide gauge observations, rainfall, ocean heat content, forest fire danger index and related variables. (6) Across a selection of tests, a simple stepladder model better represents the internal structures of warming than a simple trend – strong evidence that the climate system is exhibiting complex system behaviour on decadal timescales. This model indicates that in situ warming of the atmosphere does not occur; instead, a store-and-release mechanism from the ocean to the atmosphere is proposed. It is physically plausible and theoretically sound. The presence of steplike – rather than gradual – warming is important information for characterising and managing future climate risk.
Comments welcome: here or there. Deadline October 4.
Imagine you didn’t know anything about climate change and the greenhouse effect but were interested and you know a bit about general science. Would you accept the following story?
“Earth’s climate is a large, complex system, affected by forces that produce both linear and nonlinear responses. Shortwave radiation – basically UV – from the sun comes in and heats up the planet, producing infrared radiation. Some UV gets reflected straight back out by clouds, snow and ice and stuff. The land can heat up quite a lot, but it cools back down again and doesn’t store much. If a forest is cleared and replaced by buildings, it will warm up a bit but the effect is only local.”
“But the ocean – that’s another story. It absorbs a lot of radiation, so is taking up heat all the time. Huge streams of energy are entering and leaving the ocean store each year. Some is ‘dry’ or sensible heat, which is ordinary warmth. Some is ‘wet heat’ or evaporated moisture. Energy gets taken up when the moisture is evaporated and it will be released again when the moisture cools, condenses and then gets rained out. In this way, the oceans provide a lot of heat to the land every year, largely as rainfall and a bit of snow.”
A colleague, Celeste Young has just released a guide for adaptation practitioners: The problem solution framework: process guidance for adaptation practitioners. You can download it here: Problem Solution FINAL
This is a really useful guide that doesn’t worry too much about what climate information people have to deal with, but deals with the question – “Ok, you have decided to adapt, so how do you go about it?”
From the introduction:
The problem solution framework was developed by actively working with researchers and climate change practitioners in Australia over a number of years to assist practitioners in making sense of the information they received and how to apply it in their context. What I observed during this time was that successful practitioners in this field often intuitively used innovation techniques, but did not always recognise innovation or understand how it worked. I found that in some cases practitioners were getting stuck in the problem phase and continuing to use problem framing throughout the process, which could cause barriers to action and engagement.
What needed to be understood was the changeover between the problem and solution phases, and which work practices were best suited for the different parts of the adaptation process. I also found in some cases that practitioners were moving into the solution phase without fully understanding the nature of the problem which could lead to unrealistic expectations and poor outcomes.
An excellent briefing from Paul Rogers of the Oxford Research Group on food security and climate change is updating the current global situation with respect to recent climate events (Hat tip to Jamie Doughney). I’ll reproduce it below after making a few comments.
Most of the briefing concentrates on the conditions of the 1974 food crisis to add a historical perspective. Globally, the US and North America is in the second year of drought, looking at greatly reduced maize production and other other crops. The southwest Indian monsoon is somewhat late and currently at 17% below the 50-year average after a poor year last year. The Horn of Africa is in a delicate recovery stage after last year’s disaster, and efforts to build resilience in the region are ongoing. A recent report from scientists at the UK’s Met Office and the USA’s National Oceanographic and Atmospheric Administration (NOAA) found that the number of below average rainy seasons in East Africa could have been attributable to warming in the Indian and Western Pacific Oceans.
Rogers states that economic growth has been patchy, so that the proportion of people under food stress has not changed greatly since the 1970s. This time around though, he nominates climate change as making a significant contribution to that stress. I agree. One part of that is the asymmetric impact of warming on land affecting drier regions. This is pretty well known. The other is that he suggests climate change is accelerating:
The loss of Arctic sea in recent summers has exceeded forecasts using climate modelling and some recent events have been startling in their intensity, including the extent of the thawing of surface layers of the Greenland ice cap during the early part of July.
This is because climate change is strongly non-linear, and there is increasing evidence that the world, or at least much of the northern hemisphere, is in a warming episode similar to that experienced in 1997-98. The idea that extremes should change gradually on a smoothly changing mean climate is seriously wrong, and if the world continues to adapt based on that assumption, millions of people will continue to be at risk through insufficient adaptation efforts.
I’m champing at the bit to get back to this research because I use different methods to those of mainstream climate science (but also have a truckload of other work to do). However, both lines of research are pointing to a strong climate change signal in recent extreme events, thereby increasing scientific confidence in its conclusions.
Rogers’ briefing is reproduced below.
For those who didn’t catch it, during the week an op-ed of mine was Climate Policy will Stay a Mystery until Silent Specialists Join the Debate was published in The Age. It was based on an earlier post where I detailed the benefits of Australia’s climate policy and the tricks used by opponents to make it look more ineffective than it is likely to be. In the op-ed I ask where are the barefoot economists who will challenge untrue statements about climate and the economy? Text reproduced below (with small edits for clarity).
Rapid warming in SE Australia challenges plans to adapt gradually
Step changes in warming of a few tenths to 1°C can produce rapid changes in risks such as extreme heat and fire danger. Yet, adaptation-planning that follows the dominant model of smooth climate change makes gradual adjustments to keep up with small changes in extremes. In these circumstances, a rapid change can catch sensitive systems out. Poorly planned responses may also lead to maladaptation.
Studies of prehistoric climate change in Victoria’s western lakes imply that future changes might not be smooth. Dacre Smith's painting of Lake Gnotuk, from Views of Victoria in the steps of von Guerard.
Last Friday, the Wall Street Journal published a letter from 16 scientists entitled: No Need to Panic About Global Warming: There’s no compelling scientific argument for drastic action to ‘decarbonize’ the world’s economy.
They tried to revivify a number of zombies.
- Objecting to the statement that “The evidence is incontrovertible: Global warming is occurring” from the American Physical Society’s climate policy statement. Apparently, nothing in science is incontrovertible, not even data trending in one direction. The APS added a commentary “However, the word “incontrovertible” in the first sentence of the second paragraph of the 2007 APS statement is rarely used in science because by its very nature science questions prevailing ideas. The observational data indicate a global surface warming of 0.74 °C (+/- 0.18 °C) since the late 19th century.” Incontrovertible means there is no evidence to the contrary.
- The lack of warming over the past decade zombie.
- The CO2 is not a pollutant zombie.
- The de Freitas / Climate Research affair zombie, where a paper by Soon and Baliunas that de Freitas edited claimed that the recent warming was not unusual in the context of the past 1,000 years which they called a politically incorrect (but factually correct) conclusion. Unfortunately the paper was not factually correct and should not have been published. The Editor in Chief and three associate editors resigned, leading the publishers to revamp the journal, de Freitas losing his editorial position in the process.
- The climate change – Lysenkoism zombie.
- Climate science is at the trough zombie (follow the money).
They also claimed:
A recent study of a wide variety of policy options by Yale economist William Nordhaus showed that nearly the highest benefit-to-cost ratio is achieved for a policy that allows 50 more years of economic growth unimpeded by greenhouse gas controls.
Andrew Revkin of New York Times blog Dot Earth posted a response by Nordhaus:
The piece completely misrepresented my work. My work has long taken the view that policies to slow global warming would have net economic benefits, in the trillion of dollars of present value. This is true going back to work in the early 1990s (MIT Press, Yale Press, Science, PNAS, among others). I have advocated a carbon tax for many years as the best way to attack the issue. I can only assume they either completely ignorant of the economics on the issue or are willfully misstating my findings.