This pattern masked (my conjecture) a «background» rise in
global temperatures over that period, instead making it look like there was a rise circa 2000 - 2001 rather than 1995 - 2001.
This is currently done, as Fred says, by computing anomalies: the average
global temperature over some period is chosen to be zero and every other temperature is referred to that.
But this requires natural variability to have contributed a net negative influence on
global temperatures over that period.
If all that CO2 does is to marginally raise
global temperature over the period of a natural solar driven warming and cooling cycle then there is nothing to fear because the mitigating effect in cool periods will outweigh any discomfort from the aggravating effect at and around the peak of the warm periods.
While the AMO has not changed much in the past 10 years, the strong increase in North Atlantic temperatures between 1970 and 2000 may have contributed to the rapid rise in
global temperatures over that period, and the leveling - out of the AMO may help make the observed pause in warming more likely.
Global temperatures over this period is estimated to be 3 to 4 °C warmer than pre-industrial temperatures.
Not exact matches
For a start, observational records are now roughly five years longer, and the
global temperature increase
over this
period has been largely consistent with IPCC projections of greenhouse gas — driven warming made in previous reports dating back to 1990.
The scientists then compared their findings to
global temperatures over the same time
period.
The IPCC, in its most recent assessment report, lowered its near - term forecast for the
global mean surface
temperature over the
period 2016 to 2035 to just 0.3 to 0.7 degree C above the 1986 — 2005 level.
If this rapid warming continues, it could mean the end of the so - called slowdown — the
period over the past decade or so when
global surface
temperatures increased less rapidly than before.
According to the AAAS What We Know report, «The projected rate of
temperature change for this century is greater than that of any extended
global warming
period over the past 65 million years.»
The public, press and policy makers have been repeatedly told that three claims have widespread scientific support:
Global temperature has risen about a degree since the late 19th century; levels of CO2 in the atmosphere have increased by about 30 %
over the same
period; and CO2 should contribute to future warming.
Third, to fit
global temperatures to CO2
over a
period of 30 years and and use a linear trend to extrapolate for the next 50 years is asking for trouble.
Global mean
temperatures averaged
over land and ocean surfaces, from three different estimates, each of which has been independently adjusted for various homogeneity issues, are consistent within uncertainty estimates
over the
period 1901 to 2005 and show similar rates of increase in recent decades.
[T] he idea that the sun is currently driving climate change is strongly rejected by the world's leading authority on climate science, the U.N.'s Intergovernmental Panel on Climate Change, which found in its latest (2013) report that «There is high confidence that changes in total solar irradiance have not contributed to the increase in
global mean surface
temperature over the
period 1986 to 2008, based on direct satellite measurements of total solar irradiance.»
Results from a multiregression analysis of the
global and sea surface
temperature anomalies for the
period 1950 — 2011 are presented where among the independent variables multidecade oscillation signals
over various oceanic areas are included.
Over the same
period,
global temperature has risen markedly (top).
Using a statistical model calibrated to the relationship between
global mean
temperature and rates of GSL change
over this time
period, we are assessing the human role in historic sea - level rise and identifying human «fingerprints» on coastal flood events.
This warm phase had begun in the Cretaceous
period, peaked in the early Eocene, and continued to the end of the Eocene, when
global temperatures dropped and ice sheets formed
over the Antarctic.
Ocean
temperatures experience interannual variability and
over the past 3 decades of
global warming have had several short
periods of cooling.
Climate scientists would say in response that changes in ocean circulation can't sustain a net change in
global temperature over such a long
period (ENSO for example might raise or lower
global temperature on a timescale of one or two years, but
over decades there would be roughly zero net change).
Without mitigation of emissions, we may generate greenhouse gas concentrations and
global temperatures more akin to those of the early Paleogene,
over forty million years ago, than those of the current geological
period, the Neogene.
The public, press and policy makers have been repeatedly told that three claims have widespread scientific support:
Global temperature has risen about a degree since the late 19th century; levels of CO2 [carbon dioxide] in the atmosphere have increased by about 30 percent
over the same
period; and CO2 should contribute to future warming.
Global average surface
temperatures increased on average by about 0.6 degrees Celsius
over the
period 1956 - 2006.
The likely contributions of natural forcing and internal variability to
global temperature change
over that
period are minor (high confidence).
The link between
global temperature and rate of sea level change provides a brilliant opportunity for cross-validation of these two parameters
over the last several millenia (one might add - in the relationship between atmospheric [CO2] and Earth
temperature in the
period before any significant human impact on [CO2]-RRB-.
Current
global temperatures are warmer than about 75 % of temps
over that
period.
B. Takes an adjustment to sea
temperatures in a defined
period and implies that it impacts the
global mean
temperatures trend estimates
over the entire twentieth century.
Item 8 could be confusing in having so many messages: «It is extremely likely that more than half of the observed increase in
global average surface
temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas... The best estimate of the human - induced contribution to warming is similar to the observed warming
over this
period....
In Fig. 8, I have digitized the outer bounds of the model runs in Fig. 7, and also plotted the HadCRUT3
global annual mean
temperature anomaly
over the same
period.
Observed
global temperature increase
over this
period was ~ 0.6 C. Staying within these error bars for all individual forcings the
temperature could have decreased by 0.1 C!
Over very long time periods such that the carbon cycle is in equilibrium with the climate, one gets a sensitivity to global temperature of about 20 ppm CO2 / deg C, or 75 ppb CH4 / deg C. On shorter timescales, the sensitivity for CO2 must be less (since there is no time for the deep ocean to come into balance), and variations over the last 1000 years or so (which are less than 10 ppm), indicate that even if Moberg is correct, the maximum sensitivity is around 15 ppm CO2 / deg C. CH4 reacts faster, but even for short term excursions (such as the 8.2 kyr event) has a similar sensitiv
Over very long time
periods such that the carbon cycle is in equilibrium with the climate, one gets a sensitivity to
global temperature of about 20 ppm CO2 / deg C, or 75 ppb CH4 / deg C. On shorter timescales, the sensitivity for CO2 must be less (since there is no time for the deep ocean to come into balance), and variations
over the last 1000 years or so (which are less than 10 ppm), indicate that even if Moberg is correct, the maximum sensitivity is around 15 ppm CO2 / deg C. CH4 reacts faster, but even for short term excursions (such as the 8.2 kyr event) has a similar sensitiv
over the last 1000 years or so (which are less than 10 ppm), indicate that even if Moberg is correct, the maximum sensitivity is around 15 ppm CO2 / deg C. CH4 reacts faster, but even for short term excursions (such as the 8.2 kyr event) has a similar sensitivity.
In fact, we do in fact have NH and
global temperature reconstructions
over that
period, which show the twentieth century warming to be much faster than the prior warming as the Earth exited the LIA.
Perhaps this implies that ENSO is a leading indicator of whatever is driving
global climate
over an intermediate time
period, and the actual
temperatures is more of a lagging indicator.
The HadCRUT4 dataset, compiled from many thousands of
temperature measurements taken across the globe, from all continents and all oceans, is used to estimate
global temperature, shows that 2017 was 0.99 ± 0.1 °C above pre-industrial levels, taken as the average
over the
period 1850 - 1900, and 0.38 ± 0.1 °C above the 1981 - 2010 average.
4)
Over this
period (the past two centuries), the
global mean
temperature has increased slightly and erratically by about 1.8 degrees Fahrenheit or one degree Celsius; but only since the 1960's have man's greenhouse emissions been sufficient to play a role.
To answer the question of the Medieval Warm
Period, more than 1,000 tree - ring, ice core, coral, sediment and other assorted proxy records spanning both hemispheres were used to construct a
global map of
temperature change
over the past 1,500 years (Mann 2009).
This represents an about 53 % administrative
temperature increase
over this
period, meaning that more than half of the reported (by GISS)
global temperature increase from January 1910 to January 2000 is due to administrative changes of the original data since May 2008.
But their PNAS publication also referred to natural climate cycles, superimposed on the trend line, like ENSO and solar variability, both of which have been net contributors to
global cooling
over 1998 - 2008 [so climate skeptics can not — as they still do — point to either the Sun or El Niño to explain the world's
temperature graph
over that
period of time].
When flatlining
temperatures wreck your
global warming agenda, refusing to rise after 18 + long years in hiatus, despite record human CO2 emissions
over that same
period, simply homogenise, adjust (tamper) with the data.
Figure 6: Easterbrook's two
global temperature projections A (green) and B (blue) vs. the IPCC TAR simple model projection tuned to seven
global climate models for emissions scenario A2 (the closest scenario to reality thus far)(red) and observed
global surface
temperature change (the average of NASA GISS, NOAA, and HadCRUT4)(black)
over the
period 2000 through 2011.
As LST closely tracks air
temperatures over the instrumental
period, we can also infer that air
temperatures in this region of East Africa varied in concert with the
global average and thus were controlled primarily by the major forcings influencing
temperatures over this timescale, both natural (solar radiation, volcanism) and anthropogenic (greenhouse - gas emissions; refs 19, 20).
First, Happer mentions statistical significance, but
global surface
temperature trends are rarely if ever statistically significant (at a 95 % confidence level)
over periods as short as a decade, even in the presence of an underlying long - term warming trend, because of the natural variability and noise in the climate system.
Apparently an Australian Legislator named Stephen Fielding posted this chart and asked, «Is it the case that CO2 increased by 5 % since 1998 whilst
global temperature cooled
over the same
period (see Fig. 1)?
The warming rate
over the 40 years 1694 - 1733, demonstrated by the Central England
Temperature Record, a reasonable proxy for global temperature anomalies, was considerably greater than in any subsequent 40 - y
Temperature Record, a reasonable proxy for
global temperature anomalies, was considerably greater than in any subsequent 40 - y
temperature anomalies, was considerably greater than in any subsequent 40 - year
period.
They also looked at a
period when
global temperatures dropped 11 to 12 degrees
over a
period 52 million to 34 million years ago.
After a series of informal consultations, compromise text was introduced, which included two bullet points in the observations section, one relating to a linear trend in
global temperature increase of 0.85 °C
over the
period 1880 and 2012, when multiple datasets exist, and another, on regional trends for 1901 - 2012.
The Sea Surface
Temperature Climate Change Initiative (SST CCI) project will accurately map the surface temperature of the global oceans over the period 1991 to 2010, using observations from many
Temperature Climate Change Initiative (SST CCI) project will accurately map the surface
temperature of the global oceans over the period 1991 to 2010, using observations from many
temperature of the
global oceans
over the
period 1991 to 2010, using observations from many satellites.
«The
temperature records, that is, the «signal» of warmth that we're reconstructing for this part of the Canadian Arctic
over the past 10,000 years seems to be higher than the
global average for that
period and even higher than the Arctic average.»
Human civilization developed
over a
period of 10,000 years during which
global average surface
temperatures remained remarkably stable, hovering within one degree Celsius of where they are today.