Not exact matches
Tamsin Edwards, a climatologist at the Open University
in the UK, says it is too early to tell, since
changes in the PDO can only be detected through statistical analysis of
large amounts of data on ocean
surface temperatures.
There are strong competing effects such as
changes in the
large - scale atmospheric circulation, sea
surface temperature changes like El Niño and La Niña and the dynamics of westerly storm tracks that all interact at the mid-latitudes,» said Stanford co-author Matthew Winnick who contributed to the study with fellow doctoral student Daniel Ibarra.
As discussed
in the Climate chapter,
large - scale atmospheric circulation patterns connected to
changes in sea -
surface temperatures strongly influence natural variations
in precipitation and
temperature (e.g., Cayan et al. 1999; Mantua and Hare 2002).
Scientists use a
large drill to remove parts of the coral to analyse for information about
changes in rainfall and sea
surface temperature.
For significant periods of time, the reconstructed
large - scale
changes in the North Pacific SLP field described here and by construction the long - term decline
in Hawaiian winter rainfall are broadly consistent with long - term
changes in tropical Pacific sea
surface temperature (SST) based on ENSO reconstructions documented
in several other studies, particularly over the last two centuries.
During El Nino events the ocean circulation
changes in such a way as to cause a
large and temporary positive sea
surface temperature anomaly
in the tropical Pacific.
The substantial uncertainties currently present
in the quantitative assessment of
large - scale
surface temperature changes prior to about A.D. 1600 lower our confidence
in this conclusion compared to the high level of confidence we place
in the Little Ice Age cooling and 20th century warming.»
This conclusion has subsequently been supported by an array of evidence that includes the additional
large - scale
surface temperature reconstructions and documentation of the spatial coherence of recent warming described above (Cook et al. 2004, Moberg et al. 2005b, Rutherford et al. 2005, D'Arrigo et al. 2006, Osborn and Briffa 2006, Wahl and Ammann
in press) and also the pronounced
changes in a variety of local proxy indicators described
in previous chapters (e.g., Thompson et al.
in press).
There are two very basic answers: First, looking at
changes in data gets rid of biases at individual stations that don't
change in time (such as station location), and second, for
surface temperatures at least, the correlation scale for anomalies is much
larger (100's km) than for absolute
temperatures.
So, it follows on phtysical grounds that any
temperature change at the
surface gets amplified aloft which means that the variability
in temperature (solely the «dry» energy term) is
larger aloft than at the
surface.
The paleoclimate record (8.2 kyr, and earlier «
large lake collapses») shows a dramatic drop
in surface temperatures for a substantial period of time when the ocean circulation shuts off or
changes, but is that actually what would be expected under these warming conditions?
The paper he wrote together with Friis - Christensen
in which he found a correlation between solar activity and clouds had a «slight» flaw: it ignored that the period of the study coincided with a big El Nino, and that
large scale
changes in ocean
surface temperature are going to have an effect on cloud formation.
Before allowing the
temperature to respond, we can consider the forcing at the tropopause (TRPP) and at TOA, both reductions
in net upward fluxes (though at TOA, the net upward LW flux is simply the OLR); my point is that even without direct solar heating above the tropopause, the forcing at TOA can be less than the forcing at TRPP (as explained
in detail for CO2
in my 348, but
in general, it is possible to bring the net upward flux at TRPP toward zero but even with saturation at TOA, the nonzero skin
temperature requires some nonzero net upward flux to remain — now it just depends on what the net fluxes were before we made the
changes, and whether the proportionality of forcings at TRPP and TOA is similar if the effect has not approached saturation at TRPP); the forcing at TRPP is the forcing on the
surface + troposphere, which they must warm up to balance, while the forcing difference between TOA and TRPP is the forcing on the stratosphere; if the forcing at TRPP is
larger than at TOA, the stratosphere must cool, reducing outward fluxes from the stratosphere by the same total amount as the difference
in forcings between TRPP and TOA.
(Within the range where water vapor feedback is runaway, zero
change in external forcing»cause s» a
large change in climate; the equilibrium
surface temperature, graphed over some measure of external forcing, takes a step at some particular value.)
If the
surface temperature is slow to catch up to that imbalance then the energy imbalance remains
large, and we can have sufficient net heating to cause much faster
changes in the ice sheets than from the comparatively smaller imbalances caused by the
changes in Earth's orbit associated with the glacial periods
in the past.
The ability of a band to shape the
temperature profile of the whole atmosphere should tend to be maximum at intermediate optical thicknesses (for a given band width), because at small optical thicknesses, the amounts of emission and absorption within any layer will be small relative to what happens
in other bands, while at
large optical thicknesses, the net fluxes will tend to go to zero (except near TOA and, absent convection, the
surface) and will be insensitive to
changes in the
temperature profile (except near TOA), thus allowing other bands greater control over the
temperature profile (depending on wavelength — greater influence for bands with
larger bandwidths at wavelengths closer to the peak wavelength — which will depend on
temperature and thus vary with height.
The second aspect of climate
change that is likely affecting Alaska more and more is the apparent tendency of warming
in the Arctic and warmer sea
surface temperatures in the Pacific to contribute to
larger waves
in the jet stream.
Is the past 10 to 15 years — which have seen little net
change in the average
surface temperature of the Earth despite ever -
larger carbon dioxide emissions — an indication that climate
change will not be as bad as previously projected?
But it does say; «Natural climate variations, which tend to involve localized
changes in sea
surface temperature, may have a
larger effect on hurricane activity than the more uniform patterns of global warming...»
Many models have
large biases
in lower stratospheric water vapour (Gettelman et al., 2010), which could have implications for
surface temperature change (Solomon et al., 2010).
Large uncertainties
in surface temperature change may exist at every single grid point of the Earth.
The overall level of consistency between attribution results derived from different models (as shown
in Figure 9.9), and the ability of climate models to simulate
large - scale
temperature changes during the 20th century (Figures 9.5 and 9.6), indicate that such model differences are likely to have a relatively small impact on attribution results of
large - scale
temperature change at the
surface.
Note: The step
change (
temperature drop) at 1945 has been identified as an error in a recent Thompson et al letter to «Nature» with the title «A Large Discontinuity in the Mid-Twentieth Century in Observed Global - Mean Surface Temperat
temperature drop) at 1945 has been identified as an error
in a recent Thompson et al letter to «Nature» with the title «A
Large Discontinuity
in the Mid-Twentieth Century
in Observed Global - Mean
Surface TemperatureTemperature».
Going forwards CO2 forcing is several times
larger than the LIA solar forcing which was itself measurable
in the
surface temperature record, so we expect CO2 forcing to be measurable for sure, and yes, it will be accompanied by some effects of
changing clouds too, but we don't know which direction they would push it.
Given the vast pool of very cold water
in the deep ocean, even modest
changes in the rate it exchanges heat with the
surface can produce
large changes in temperature without any
change in the planetary radiative balance.
Even
in areas where precipitation does not decrease, these increases
in surface evaporation and loss of water from plants lead to more rapid drying of soils if the effects of higher
temperatures are not offset by other
changes (such as reduced wind speed or increased humidity).5 As soil dries out, a
larger proportion of the incoming heat from the sun goes into heating the soil and adjacent air rather than evaporating its moisture, resulting
in hotter summers under drier climatic conditions.6
We further estimate that,
in most northern hemispheric regions, these
changes in the likelihood of extreme summer mean WBGT are roughly an order of magnitude
larger than the corresponding
changes in the likelihood of extreme hot summers as simply measured by
surface air
temperature.
This may seem like a small number compared to
changes in daily
temperature however to put it into comparison how small global
temperature changes can have a
large effect, if the Earth's
surface temperature was lowered by 5 ⁰ C it would be
in a full ice age.
We use a one - dimensional radiative - convective model for the atmospheric thermal structure to compute the
change in the
surface temperature of the earth for
large assumed increases
in the trace gas concentrations; doubling the N2O, CH4, and NH3 concentrations is found to cause additive increases
in the
surface temperature of 0.7 °, 0.3 °, and 0.1 ° K, respectively.
The slowed
surface warming is due
in large part to
changes in ocean cycles, particularly
in the Pacific Ocean, causing more efficient ocean heat uptake, thus leaving less heat to warm
surface temperatures.
Dessler (2011) used observational data (such as
surface temperature measurements and ARGO ocean
temperature) to estimate and corroborate these values, and found that the heating of the climate system through ocean heat transport was 20 times
larger than TOA energy flux
changes due to cloud cover over the period
in question.
This conclusion has subsequently been supported by an array of evidence that includes the additional
large - scale
surface temperature reconstructions and documentation of the spatial coherence of recent warming described above (Cook et al. 2004, Moberg et al. 2005b, Rutherford et al. 2005, D'Arrigo et al. 2006, Osborn and Briffa 2006, Wahl and Ammann
in press) and also the pronounced
changes in a variety of local proxy indicators described
in previous chapters (e.g., Thompson et al.
in press).
The NAO's prominent upward trend from the 1950s to the 1990s caused
large regional
changes in air
temperature, precipitation, wind and storminess, with accompanying impacts on marine and terrestrial ecosystems, and contributed to the accelerated rise
in global mean
surface temperature (e.g., Hurrell 1996; Ottersen et al. 2001; Thompson et al. 2000; Visbeck et al. 2003; Stenseth et al. 2003).
This conclusion has subsequently been supported by an array of evidence that includes both additional
large - scale
surface temperature reconstructions and pronounced
changes in a variety of local proxy indicators, such as melting on icecaps and the retreat of glaciers around the world, which
in many cases appear to be unprecedented during at least the last 2000 years.
Importantly, the
changes in cereal yield projected for the 2020s and 2080s are driven by GHG - induced climate
change and likely do not fully capture interannual precipitation variability which can result
in large yield reductions during dry periods, as the IPCC (Christensen et al., 2007) states: ``... there is less confidence
in the ability of the AOGCMs (atmosphere - ocean general circulation models) to generate interannual variability
in the SSTs (sea
surface temperatures) of the type known to affect African rainfall, as evidenced by the fact that very few AOGCMs produce droughts comparable
in magnitude to the Sahel droughts of the 1970s and 1980s.»
The use of even more recently computer - reconstructed total solar irradiance data (whatever have
large uncertainties) for the period prior to 1976 would not
change any of the conclusions
in my paper, where quantitative analyses were emphasized on the influences of humans and the Sun on global
surface temperature after 1970 when direct measurements became available.
Change in entropy at the
surface is a
large negative value, because we have to consider the source
temperature of the energy.
The basic conclusion of Mann et al. (1998, 1999) that the late 20th century warmth
in the Northern Hemisphere was unprecedented during at least the last 1,000 years has subsequently been supported by an array of evidence that includes both additional
large - scale
surface temperature reconstructions and pronounced
changes in a variety of local proxy indicators
Judith writes: «Relative to the broader issue of attribution, which are at the heart of skeptical concern, details of the
surface temperature record don't play a terribly
large role
in most people's skepticism about climate
change.»
Also Wentz neglects the fact that small
changes in relative humidity or difference between
surface and near air
temperatures can result
in large changes in evaporation rates based on their equation (1) which determines evaporation rate.
The
large interannual to decadal hydroclimatic variability
in winter precipitation is highly influenced by sea
surface temperature (SST) anomalies
in the tropical Pacific Ocean and associated
changes in large - scale atmospheric circulation patterns [16].
«From 1910 - 1949 (pre-agricultural development, pre-DEV) to 1970 - 2009 (full agricultural development, full - DEV), the central United States experienced
large - scale increases
in rainfall of up to 35 % and decreases
in surface air
temperature of up to 1 °C during the boreal summer months of July and August... which conflicts with expectations from climate
change projections for the end of the 21st century (i.e., warming and decreasing rainfall)(Melillo et al., 2014).»
Had Hansen used a climate model with a climate sensitivity of approximately 3.4 °C for 2xCO2 (at least
in the short - term, it's likely
larger in the long - term due to slow - acting feedbacks), he would have projected the ensuing rate of global
surface temperature change accurately.
Although documented
changes in global
surface temperatures during the Holocene and Common era are relatively small, the concomitant
changes in OHC are
large.»
Table 1 shows the resulting contributions to the global
surface temperature changes which are illustrated graphically
in Figure 1 [Note: click on Table 1 for a
larger version].
It may not be relevant but it should be pointed out that the
changes in surface temperature during the period
in question have a very
large uncertainty.
It would clearly be inappropriate to regress
surface temperature changes on forcing
changes for the reasons you give, since relative uncertainty
in forcing
changes is much
larger than that
in temperature changes.
A small localized
change in surface temperature can cause a convection burst (thunderstorm) and a
large increase
in convection height, improving both reflection of incoming solar radiation, and conveying sensible heat to a higher altitude where it can then escape to space via radiative processes with far less interference.
http://www.agci.org/docs/lean.pdf «Global (and regional)
surface temperature fluctuations
in the past 120 years reflect, as
in the space era, a combination of solar, volcanic, ENSO, and anthropogenic influences, with relative contributions shown
in Figure 6.22 The adopted solar brightness
changes in this scenario are based on a solar
surface flux transport model; although long - term
changes are «50 %
larger than the 11 - year irradiance cycle, they are significantly smaller than the original estimates based on variations
in Sun - like stars and geomagnetic activity.
Climate model simulations indicate that
changes in solar radiation a few times
larger than those confirmed
in the eleven - year cycle, and persisting over multi-decadal time scales, would directly affect the
surface temperature.