Re. Response to 3 questions, Q2.
Is it the case that the rate and magnitude of warming between 1979 and 1998 (the late 20th century phase of global warming) was not unusual in either rate or magnitude as compared with warmings that have occurred earlier in the Earth's history?
Correct answer - Yes.
While the Earth's temperature has been warmer in the geological past than it is today, the magnitude and rate of change is unusual in a geological context.
The Little Ice Age was an usual event in its depth and brevity. A comparable event has not been found. Comparing emergence to real ice age events is not appropriate and to say the rapidity of emergence is unusual is to state belief thus:
Evidence from ice cores shows that between ice ages and warm inter-glacial periods temperatures increased by 4 to 7°C. However this was a gradual process taking approximately 5,000 years. More rapid changes in temperature, such as those associated with the well-known Dansgaard-Oeschger events during the last ice age, are not global but rather highly regional in character. Globally, the Earth has already experienced warming of 0.76°C since 1850, a very rapid change in geological terms.
Ice cores are also regional. Cores of ice laid down in sub zero temperatures record discrete events (snow) that at the very least have a problem of resolution due to compression causing smoothing or smearing that defies identification of rapid events. To suggest certain knowledge is simply propaganda. Vostok ice can take thousands of years to close (cease interacting with air) due to the lack of snowfall. It is arid.
In terms of timescales of importance for humans, the last 2,000 years are most relevant, because this is the period over which our civilisations have developed. 2 steps forward in warm eras and one step back in cool eras.
The only reference to historic and prehistoric times we have is
proxies that don't give good resolution. The best that can be
said is there have been much hotter times and with low CO2
and much colder times and with high CO2. The warmest
temperature measured at Vostok in recent times is -12.2°C.
(Image from Globalwarmingart)
The figure below shows an 1800-year northern hemisphere air temperature record including a variety of estimates of past temperature trends. The light grey shading indicates the uncertainties surrounding these estimates and thus represents the envelope of natural variability over the past 1800 years. The red line at the right is the instrumental record since 1850. The broken red line is the "committed" additional temperature rise due to the thermal inertia of the ocean.
This highly contested claim was covered in "Re. response to 3 questions. Q1". The relevant links were "anomalous-spike-in-ocean-heat-content", "Have Changes In Ocean Heat Falsified The Global Warming Hypothesis?" and "Comments On A New Paper “Global Ocean Heat Content 1955–2008 In Light Of Recently Revealed Instrumentation Problems".
Even without this additional rise, the current observed temperature is now outside the envelope of natural variability over the past 1800 years and thus would certainly be considered "unusual".
Trends in Northern Hemisphere air temperature for the past 1800 years.
Note that this is the top panel of Fig T.S 20 of the AR4 WG1.
Depending on the choice of proxies of course. Has no-one told
the Senator the hockey stick was busted not least by NAS?
(Also commented on here.)
Ongoing research by a variety of contributors not only prove the
global extent, they also strongly support warming at least
as pleasant as modern day's.
Proxies, decide on your case, choose your proxy. As with models
there is a proxy that proves every condition conceivable.
Vostok though is certainly reliable.
Isn't it? Which one is faulty (and how/why)?
Both images and that below came from an excellent article
that discusses proxy variation and especially why hockey stick
types based on tree ring data are far from appropriate for use
by an organisation that has a shred of integrity.
The final example I'll show supports the MWP temperature
being comparable to present times.
(Briffa’s 2001 all tree ring proxy data, compared with non tree
The next article discusses MWP as a solar driven phenomenon
and cites a number of papers.
Medieval Warm Period (Solar Influence - Temperature)
The Medieval Warm Period Project lays to rest the fancy that
the MWP was regional.
It is unnecessary to prove the global extent of the LIA, it is
accepted that it affected the N. hemisphere and that is where
the most pleasant global warming has occurred.
That the MWP was as pleasantly warm and not due to CO2 is
sufficient to cast reasonable doubt on any IPCC selected proxy
support of their position.
If the warming was not unusual, why is it perceived to have been caused by humans carbon dioxide emissions;
The correct answer is - justification of existence, justification of funding and achievement of agenda, profit being one of the many.
and in any event, why is warming a problem if the Earth has experienced similar warmings in the past?
The correct answer is - Polar bears don't look as pretty on bare earth.
As noted above, the current warming is unusual as past changes have been triggered by natural forcings whereas there are no known natural climate forcings, such as changes in solar irradiance, that can explain the current observed warming of the climate system. It can only be explained by the increase in greenhouse gases due to human activities.
The aforesaid is unsubstantiated opinion. Cloudiness, water vapour, changing currents in the air and water, ocean oscillations, ozone, methane levels, aerosols, biomass expansion, urban heat islands etc. etc. etc. all contribute to warming. Not least solar influence that is the only source that can actually raise the energy available in the system is gaining increasing attention.
Image from Ice cap used to illustrate the paper "Evidence for a solar signature in 20th-century temperature"
Meanwhile on another planet: .
The greenhouse effect is a well-understood physical phenomenon, like gravity.
The hypothesised incorrectly named "greenhouse" effect is well understood. There is scant real world observational evidence to support it and peer reviewed science that contests it.
Greenhouse gases have a known ability to absorb heat emitted from the Earth's surface and re-emit it in the lower atmosphere.
Greenhouse gases have an estimated ability to absorb energy (dependent on ambient temperature) of low frequencies emitted from the Earth's surface that escapes the troposphere in various ways at various frequencies due to various factors such as friction and collision. Energy in the lower atmosphere is in constant flux between energy forms.
The net effect - measured as "radiative forcing" - is to increase the heat content at the Earth's surface.
The net effect is "radiative forcing" that is an estimate of how much of the estimated energy that is radiated from the Earth's surface is intercepted by the atmosphere. The calculations use hypothetical numbers as high as 41% of the Earth's total energy emission is transmitted as infrared. That is very, very high and is guessed so to produce the volume necessary to make CO2 a significant GHG. Real world measurement of IR emission by the surface, especially in CO2's range has never been undertaken despite its ease because? Satellite measurements are of IR that is not intercepted. A value for emission by the surface is assumed.
By ignoring other important methods of conveying energy from the surface to the air, not least evaporation, convection, conduction: Radiative forcing is the common currency for the effect of all factors that influence the heat content at the Earth's surface - solar irradiance, surface reflectivity, greenhouse gas concentrations, and so on. Analysis (of modelling?) of the climatic shift between the last ice age and the present warm period gives the likely wrong quantitative relationship between the change in radiative forcing and the resulting change in global air temperature because the numbers are assumed due to lack of data; this relationship includes all known feedbacks within the climate system, the value of those whose value isn't known being assumed, in an empirical way that is derived without using models (guessed?). Applying (force fitting) this relationship to the post-1850 warming shows that the magnitude of the warming at equilibrium (that is when the system settles into a stable state) is in proportion to the assumed change in radiative forcing, which in turn is largely due to (piracy, the cost of postage and) the increasing concentration of greenhouse gases (that is, solar irradiance and surface reflectivity have not changed significantly over this period on another planet whilst here on Earth solar irradiance increased throughout last century and albedo changed greatly every year between summer and winter and decade to decade).
Correlation does not prove causation. Besides, CO2 does not correlate.
The volume and effects of cloud, aerosols and ozone that regulate incoming solar radiation, of water vapour that is the main regulator of Earth radiation, the variation and effect of albedo such as ice, crops, water, the values for energy leaving the Earth's surface by conduction, convection, evaporation, radiation etc. are unknown. They have to be guessed, input to models and jiggled to produce a result that is claimed to be of value.
Still on another planet:
The evidence is thus very strong that the post-1850 warming trend is primarily caused by the increasing concentration of greenhouse gases in the atmosphere due to human activities.
The reason that the post-1850 warming trend is believed to be important is because it is believed to be moving the Earth outside of the selected proxy derived climatic envelope - the selected proxy derived patterns of natural variability - within which contemporary civilisation has developed and thrived and within which the ecosystems on which we depend have evolved. For example, it is believed that many plants and animals will be unable to adapt quickly enough to the warming trend (i.e. warmer summer evenings, shorter winters), believed to be placing them at risk of extinction. The increased temperature of summer evenings and winter will also alter natural systems such as the hydrological cycle, changing the rainfall patterns that constantly alter without help from humans on which humans have become dependent.
That contradicts the logic that says longer growing seasons with higher productivity due to higher CO2 levels makes for higher crop yields, extends habitat that increases wildlife numbers and makes almost everyone better off than in a cooling climate.
(Selected) Research shows that Australia is highly vulnerable to the impacts of climate change and that these impacts will become increasingly severe over time. River flow in the Murray-Darling Basin may decline by 10 to 25 percent by 2050 and by 2100 irrigated agriculture may decline by 92 percent. The Garnaut Review based on biased IPCC science also found that the climate change impacts on infrastructure will have a significant effect on Australia's output and consumption of goods and services, and that the costs of adaptation could be high. In summary, if the current warming trend is allowed to continue unabated (said as if we could influence it without a shred of evidence that we can) through the rest of this century and beyond, the risk of impacts to which contemporary society cannot adapt rises sharply.
Prof. R. M. Carter (PhD BSc) in his Sept 2008 essay wrote;
Before human-caused global warming can become an economic problem, it first has to be identified by scientific study as a dangerous hazard for the planet, distinct from natural climate change.
This notwithstanding, a number of distinguished economists have recently written compendious papers or reports on the issue, for example Nicholas Stern (2006) and William Nordhaus (2007); in Australia, Ross Garnaut is currently undertaking a similar analysis. These persons, and many other public commentators and politicians as well, have indicated that they accept that there is a scientific consensus that dangerous, human-caused global warming is occurring, as set by the views and advice of the Intergovernmental Panel on Climate Change (IPCC).
The IPCC is the United Nations body whose second chairman, John Houghton, wrote in 1994 that ‘unless we announce disasters, no one will listen’. From that point forward, it was obvious that IPCC pronouncements needed to be subjected to independent critical analysis;
Science funding has for decades been biased towards efforts that support the AGW hypothesis. The IPCC has selected science that supports its position. Contradictory science has been suppressed or ignored. The notion CO2 as a gas that is harmful to climate in tiny volumes remains devoid of observational support after decades of research by the best minds. That is a powerful indication that there is none to be found. Average temperature increased. A combination of increased input and a planet response is all that is certain. That greenhouse gases do not produce energy is a given. They cannot raise the level of existing energy, merely slow its escape fractionally. IR travels at the speed of light. Allocation of responsibility is the purest of conjecture. STILL.
Footnote. The radiance from the surface does not magically raise the temperature by CO2's increased absorption of it. The very cool IR in CO2's ranges is absorbed statiscally 100% very near the surface, likely 10-20 metres by pre-war levels. More CO2 reduces that height. It doesn't increase the energy.
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