Archive for the ‘Climate observations’ Category
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.”
As a result of the statement I made regarding the BoM Annual Climate Statement 2013, I was asked to do a radio interview on ABC drivetime radio in WA, so had a close look at the WA numbers to provide some local background. Average temperature was 0.98°C warmer than the 1961-90 average, the next highest being +0.93°C in 1998. Maximum temperature was also the warmest at +1.11°C compared to +1.00°C in 1994. Minimum temperature was not quite the warmest on record.
But the big shock I got was when I looked at sea surface temperatures (SSTs) for south-west WA. Have a look at this graph (note that 2013 isn’t up there yet due to a delay in processing):
On Friday Jan 3, the Australian Bureau of Meteorology released its Annual climate statement 2013. The headline statements include:
Data collected and analysed by the Bureau of Meteorology show that 2013 was Australia’s warmest year on record while rainfall was slightly below average nationally.
- Summer 2012–13 was the warmest on record nationally, spring was also the warmest on record and winter the third warmest
- Overall, 2013 was Australia’s warmest year on record: annual national mean temperature was +1.20°C above average
- All States and the Northern Territory ranked in the four warmest years on record
- Nationally-averaged rainfall was slightly below average for the year, with 428 mm (1961–1990 average 465 mm)
- Rainfall was mostly below average for the inland east and centre, and above average for the east coast, northern Tasmania and parts of Western Australia
The statement was widely reported – two good summaries by the BoM crew and Lewis and Karoly can be found on The Conversation. One of the biggest talking points was that 2013 was a normal year meteorologically – no El Niño in sight – but the temperature was still a record. Much of the reporting in Australia pointed out the disjuncture between observations and current government policy. The Australian Science Media Centre also had a rapid round-up that included some words from me.
The following statements are typical of the gradualist adaptation narrative:
- Within limits, the impacts of gradual climate change should be manageable.
- Therefore, climate change adaptation can be understood as: (a) adapting to gradual changes in average temperature, sea level and precipitation.
- Gradual climate change allows for a gradual shift in the mix of crops and to alternative farming systems.
So why are Gauss and Newton in the bath and Ed Lorenz in the hot tub?
During the last weekend in July, Perth experienced an unusually high number of deaths, putting pressure on the state’s mortuaries. All facilities are full, according to the ABC.
Curiosity piqued, I checked Perth’s weather data for unseasonal cold. Sure enough, during June and July, Perth and the rest of south west WA had experienced cold conditions, not seen in Perth for 13 years and longer elsewhere. This linked article was published in mid July. In the last three weeks of July, daily temperatures were below 10 degrees on 3, 4 and 3 days, respectively preceding the last weekend of July.
Was it the the poor, the aged and the infirm filling the mortuaries, after repeated, unseasonal cold snaps? Has an overall warmer climate not insulated people from such events? The average temperature at Perth Airport is 13°C and for July was 11°C; perhaps there are some bad respiratory diseases around making things worse.
Cold remains dangerous for the vulnerable in southern winters. At this range of temperature, contrasts in temperature are the largest risk to vulnerable people, rather than absolute temperatures themselves.
After me getting an op-ed in The Age representing real climate science and policy, it’s time for some asshattery, c/- both the Melbourne Age and the Sydney Morning Herald. The Fairfax press has decided to redress the balance of knowledge with some agnotogeny* from Dr David Evans. From his tagline:
Dr David M. W. Evans is a mathematician and engineer who consulted full-time for the Australian Greenhouse Office (now the Department of Climate Change) from 1999 to 2005. He says he changed from being a warmist to a sceptic after ”evidence supporting the idea that CO2 emissions were the main cause of global warming reversed itself from 1998 to 2006”.
Oh purleeze. Read the rest of this entry »