Sentences with phrase «in orbital forcing»

He doesn't identify eccentricity as such in the title of the paper, but it is there in his orbital forcing model, as the amplitude modulation of precession, and needed for his model to work.

But that slow lag may be only because the imbalance in the orbital forcing case is so small — 1 W / m ^ 2 at most over a thousand years or so.

So albedo change (owing to changes in orbital forcing, which is what melts the ice sheets) was comparable to, and probably larger than, the CO2 change.

Predicted changes in orbital forcing suggest that the next glacial period would begin at least 50,000 years from now, even in absence of human - made global warming (see Milankovitch cycles).

A prime example: Small perturbations in orbital forcings resulting in vast ice ages could not have occurred without strong feedbacks.

Not exact matches

Earlier studies on the sensitivity of tropical cyclones to past climates have only analyzed the effect of changes in the solar radiation from orbital forcing on the formation of tropical cyclones, without considering the feedbacks associated to the consequent greening of the Sahara.

These forces also cause the brain to move in a swirling fashion and contact the inner prominence of the skull, particularly the petrous and orbital ridges and the wings of the sphenoid.

In the study, researchers analyzed a series of transient Coupled General Circulation Model simulations forced by changes in greenhouse gases, orbital forcing, meltwater discharge and the ice - sheet history throughout the past 21,000 yearIn the study, researchers analyzed a series of transient Coupled General Circulation Model simulations forced by changes in greenhouse gases, orbital forcing, meltwater discharge and the ice - sheet history throughout the past 21,000 yearin greenhouse gases, orbital forcing, meltwater discharge and the ice - sheet history throughout the past 21,000 years.

Indeed, its a very important paper in the history of climate, linking observed cycles in ocean sediment cores to orbital forcing periodicities.

This may help explain some of the changes that are not explained by the orbital curves in the other thread, especially the initiation of warming and cooling since the GCR effects can be much more powerful (partly forcing as postulated in the paper, but also amplification of the weaker orbital forcing).

I was recently asked to explain why we can use the paleo - climate record this way when it is clear that the greenhouse gas changes (and ice sheets and vegetation) in the past were feedbacks to the orbital forcing rather than imposed forcings.

Several factors affect these cycles, but they are ultimately determined by orbital forcing — the Sun's radiation received by the Earth due to variations in the Earth's orbit in the solar system.

While Milankovitch forcing predicts that cyclic changes in the Earth's orbital parameters can be expressed in the glaciation record, additional explanations are necessary to explain which cycles are observed to be most important in the timing of glacial — interglacial periods.

He then uses what information is available to quantify (in Watts per square meter) what radiative terms drive that temperature change (for the LGM this is primarily increased surface albedo from more ice / snow cover, and also changes in greenhouse gases... the former is treated as a forcing, not a feedback; also, the orbital variations which technically drive the process are rather small in the global mean).

[Response: The loop doesn't, but the thing that starts the loop can change direction and as long as the entire feedback loop is not unstable, you simply have an amplified response to the drivers (in this case, orbital forcing).

From what I read (and I am only an amateur) orbital forcings are too slow to be a factor in sub-centennial processes.

So here's an attempt: When temperatures change because of an orbital forcing, you've got a strong CO2 feedback because the CO2 in the atmosphere was in equilibrium with the CO2 in the oceans before temperatures changed.

The major mid-Holocene forcing relative to the present was due to orbital perturbations that led to large changes in the seasonal cycle of insolation.

Onset of deglacial warming in West Antarctica driven by local orbital forcing.

The response of that model to volcanic forcings, the last ice age, changes in orbital parameters etc. are all «out - of - sample» tests that are not fixed by adjusting parameters.

Indeed, its a very important paper in the history of climate, linking observed cycles in ocean sediment cores to orbital forcing periodicities.

Some other forcings have a very small global radiative forcing and yet lead to large impacts (orbital changes for instance) through components of the climate that aren't included in the default set - up.

I was recently asked to explain why we can use the paleo - climate record this way when it is clear that the greenhouse gas changes (and ice sheets and vegetation) in the past were feedbacks to the orbital forcing rather than imposed forcings.

I don't think there was much prior uncertainty in the literature over the general notion that orbital forcing changes were an initiating factor and that consequent rises in CO2 contributed a major subsequent warming influence, but the timing (regional vs global) and the interaction between the hemispheres has not been well illuminated.

[Response: Similar to your first point — coherent statistics over time periods, robust patterns of teleconnections, process by process similarities, coherent emergent properties, quantitative matches in response to large perturbations (volcanoes, orbital forcing, continental configurations etc.).

Although the primary driver of glacial — interglacial cycles lies in the seasonal and latitudinal distribution of incoming solar energy driven by changes in the geometry of the Earth's orbit around the Sun («orbital forcing»), reconstructions and simulations together show that the full magnitude of glacial — interglacial temperature and ice volume changes can not be explained without accounting for changes in atmospheric CO2 content and the associated climate feedbacks.

The results of these simulations show that dust − climate feedbacks, perhaps set off by orbital forcing, push the system in and out of extreme cold conditions such as glacial maxima.

Since the volume of ice at risk under BAU is within a factor of two of the volume of ice at risk during a deglaciation under orbital forcing, while the forcing is much more rapidly applied under BAU, looking at sea level rise rates in the paleo - record might actually be considered a search for lower limits on what to expect if reticence did not run so strongly in our approach.

Interesting — I just (last night) emailed [email protected], offering to become involved here, and mentioned the conclusion of the Loutre and Berger paper, that orbital forcing parameters will next be conducive to widespread polar ice accumulation in about 60,000 years.

The important point here is that a small external forcing (orbital for ice - ages, or GHG plus aerosols & land use changes in the modern context) can be strongly amplified by the positive feedback mechanism (the strongest and quickest is atmospheric water vapor - a strong GHG, and has already been observed to increase.

This may then lead to additional changes, for example, the incorporation of ozone feedbacks to solar changes, or the calculation of vegetation feedbacks to orbital forcing — which in each case improved the match to the observations.

[Response: the Milankovitch timescale is long and the forcing barely varies due to orbital changes over 100 years so no, they aren't included (they would be for people modelling the last glacial maximum); solar forcing is modelled by change in total solar irradiance (probably as a total number; not sure if changes at different wavelengths are included)-- William]

And yes, there is such evidence — in the predicted response to volcanic forcing, the ozone hole, orbital variations, the sun, paleo - lake outbursts, the response to ENSO etc. that all show models matching the observations skillfully (which is not to say they match perfectly).

So in a nutshell and roughly speaking, the grand yet unintentional experiment we're running today has already been performed albeit w / the surrogate input of orbital forcing (if that's the correct way to put it) to induce the disappearance of the WAIS.

There is no modelling of any orbital variations in incoming energy, either daily, yearly or long term Milankovitch variations, based on the assumption that a global yearly average value has a net zero change over the year which is imposed on the energy forcing at the TOA and the QFlux boundary etc..

They are not tuned to trends, events (such as Pinatubo), paleo - climates (6kyr BP, LGM, 8.2 kyr event, D / O events, the PETM, the Maunder Minimum or the Eocene), other forcings (solar, orbital etc.)-- thus every match to those climate changes is «out of sample» in the sense you mean.

(Orbital forcing doesn't have much of a global annual average forcing, and it's even concievable that the sensitivity to orbital forcing as measured in terms of global averages and the long - term response (temporal scale of ice sheet response) might be approaching infinity or even be negative (if more sunlight is directed onto an ice sheet, the global average albedo might increase, but the ice sheet would be more likely to decay, with a global average albedo feedback that causes warming).

Since we can not examine the real world in the absence of forcings (there is always solar variability, volcanic eruptions, orbital forcing and random events like asteriod impacts), it is a valid working hypothesis to assume the models are reasonable.

It's the same series of an initial forcing (change in insolation due to Milankovitch orbital cycles) being amplified by reinforcing feedbacks (change in albedo, change in temperature and partial pressure regulating both CO2 and H2O), but in reverse from an exit from a glacial period.

Just a quick note to say that the paleoclimate data for earlier warm periods 125,000 years ago and even 8 - 10,000 years ago in northern Alaska (paleoclimate warmer than now, [from] different forcings) document the northward advance of the treeline from Nome to Barrow, Alaska, and the Canadian border at different times of change in Earth's orbital parameters (without a significant change in CO2).

With a different overall climatic state or geography, the system might be considerably less sensitive to orbital forcing (obviously it has been less sensitive; orbital forcing has been going on throughout Earth's history (modulated by tidally - induced changes in Earth's rotation and the moon's orbit)-RRB-.

@ 31: Also suggestive (but hardly conclusive) on Milankovich, Jochum et al 2011 (draft paper) got glacial inception in a CCSM4 model by subjecting it to orbital forcings from 115 kya.

Now one way to study this is to take the average temperature of each millenium of the record: doing so shows the most recent millenium was the coolest and the one just previous next so; this is in keeping with orbital forcing theory.

In a short piece in the PAGES Newsletter, George Denton, Wally Broecker and I linked this excess ice and orbital forcing through ocean circulation to control of CO2, and others are surely thinking along the same lineIn a short piece in the PAGES Newsletter, George Denton, Wally Broecker and I linked this excess ice and orbital forcing through ocean circulation to control of CO2, and others are surely thinking along the same linein the PAGES Newsletter, George Denton, Wally Broecker and I linked this excess ice and orbital forcing through ocean circulation to control of CO2, and others are surely thinking along the same lines.

In the past, orbital forcing's, solar changes and other things have been the big drivers.

For the mid-Holocene, coupled climate models are able to simulate mid-latitude warming and enhanced monsoons, with little change in global mean temperature (< 0.4 °C), consistent with our understanding of orbital forcing.

The conditions of this orbital climate forcing are similar to those of today's interglacial period1, 2, and they rendered the climate susceptible to other forcing — for example, to changes in the level of atmospheric carbon dioxide.

One has to look to the other macroscopic force which is conspicuously absent from the GHG assertions (can't call the «equations» because such don't exist), gravity, to explain the 3 %, in the case of Earth, and 125 %, in the case of Venus, greater surface than orbital temperatures (take those figures to the 4th power for equivalent energy densities) seen in all planetary atmospheres, and indeed all gravitational wells.

If Northern Hemisphere temperatures have been in an overall cooling trend for two millennia due to «orbital forcing» (i.e. reduced solar irradiance), then the burden of proof becomes greater on those who attribute the warmth of recent decades to solar variability rather than rising greenhouse gas concentrations.

Especially a kick of 2 W / m2 in a century which is a much higher rate of change than the orbital forcing that is measured in W / m2 per millennium.