Sentences with phrase «variation in past centuries»

The actual prevailing view of the paleoclimate research community that emerged during the early 1990s, when long - term proxy data became more widely available and it was possible to synthesize them into estimates of large - scale temperature changes in past centuries, was that the average temperature over the Northern Hemisphere varied by significantly less than 1 degree C in previous centuries (i.e., the variations in past centuries were small compared to the observed 20th century warming).

4 Dec 2004 Temperature Variations in Past Centuries and the so - called «Hockey Stick» http://www.realclimate.org/index.php?p=7

Not exact matches

Over the past quarter century the level of the fed funds rate has explained nearly 50 % of the variation in stock / bond correlations, according to Bloomberg data.

But as I noted last week (see Two Point Three Sigmas Above the Norm), nominal growth and interest rate variations have historically canceled out over the past century, with little effect on the accuracy of our valuation estimates — matched reductions in the growth rate and the discount rate really don't affect fair value.

Rather than using complex computer models to estimate the effects of greenhouse - gas emissions, Lovejoy examines historical data to assess the competing hypothesis: that warming over the past century is due to natural long - term variations in temperature.

Variations in the Sun's brightness are known to have played a part in global warming over the past few centuries.

However, unlike the climate model simulations, the new precipitation reconstruction does not show an increase of wet and dry anomalies in the twentieth century compared to the natural variations of the past millennium.

2) A better ability to constrain climate sensitivity from the past century's data 3) It will presumably be anticorrelated with year to year variations in global surface temperature that we see, especially from El Ninos and La Ninas, which will be nice whenever we have a cool year and the deniers cry out «global warming stopped!».

In fact, scientists have long recognized the importance of solar variability as one of the factors governing climate (see the very scholarly review of the subject by Bard and Frank, available here at EPSL or here as pdf) An understanding of solar variability needs to be (and is) taken into account in attribution of climate change of the past century, and in attempts to estimate climate sensitivity from recent climate variationIn fact, scientists have long recognized the importance of solar variability as one of the factors governing climate (see the very scholarly review of the subject by Bard and Frank, available here at EPSL or here as pdf) An understanding of solar variability needs to be (and is) taken into account in attribution of climate change of the past century, and in attempts to estimate climate sensitivity from recent climate variationin attribution of climate change of the past century, and in attempts to estimate climate sensitivity from recent climate variationin attempts to estimate climate sensitivity from recent climate variations.

Over the past quarter century the level of the e BoC overnight rate has explained nearly 29 % of the variation in stock / bond correlations, according to Bloomberg data.

Over the past quarter century the level of the fed funds rate has explained nearly 50 % of the variation in stock / bond correlations, according to Bloomberg data.

2) A better ability to constrain climate sensitivity from the past century's data 3) It will presumably be anticorrelated with year to year variations in global surface temperature that we see, especially from El Ninos and La Ninas, which will be nice whenever we have a cool year and the deniers cry out «global warming stopped!».

Records of tree - ring characteristics such as their width (TRW) and density (usually the maximum density of the wood formed towards the end of the growing season — the «maximum latewood density» — MXD) are widely used to infer past variations in climate over recent centuries and even millennia.

Mike's work, like that of previous award winners, is diverse, and includes pioneering and highly cited work in time series analysis (an elegant use of Thomson's multitaper spectral analysis approach to detect spatiotemporal oscillations in the climate record and methods for smoothing temporal data), decadal climate variability (the term «Atlantic Multidecadal Oscillation» or «AMO» was coined by Mike in an interview with Science's Richard Kerr about a paper he had published with Tom Delworth of GFDL showing evidence in both climate model simulations and observational data for a 50 - 70 year oscillation in the climate system; significantly Mike also published work with Kerry Emanuel in 2006 showing that the AMO concept has been overstated as regards its role in 20th century tropical Atlantic SST changes, a finding recently reaffirmed by a study published in Nature), in showing how changes in radiative forcing from volcanoes can affect ENSO, in examining the role of solar variations in explaining the pattern of the Medieval Climate Anomaly and Little Ice Age, the relationship between the climate changes of past centuries and phenomena such as Atlantic tropical cyclones and global sea level, and even a bit of work in atmospheric chemistry (an analysis of beryllium - 7 measurements).

If there was more natural variation in the past millenia, specifically due to solar changes, then that goes at the cost of the GHG / aerosol combination, as both are near impossible to distinguish from each other in the warming of the last halve century... Solar activity has never been as high, and for an as long period, as current in the past millenium (and even the past 8,000 years).

For the station nearest my home, the range (max less min) in annual average temperature for the past century is just 3.3 C. Can't say whether 1C warming matters in any tangible way, at this particular spot, but it's certainly large compared to the variation observed over the last century.

But as we started to try to piece together the puzzle of what those data were telling us, they also were telling us about natural variations in temperature in the past and how they compared to the warming trends of the past century.

This section focuses on global and regional sea level variations, over time spans ranging from the last decade to the past century; a brief discussion of sea level change in previous centuries is given in Section 5.5.2.4.

Member of the team Alena Kimbrough says, «We've shown ENSO is an important part of the climate system that has influenced global temperatures and rainfall over the past millennium... Our findings, together with climate model simulations, highlight the likelihood that century - scale variations in tropical Pacific climate modes can significantly modulate radiatively forced shifts in global temperature.»

You can also look at the growth rings in the oldest trees and in pieces of wood that have been preserved from centuries past, and try to untangle how much of the variation in growth per year is due to temperatures versus rain, fertilization, disease, etc..

States that geological records of past climates have shown century - long variations in TC numbers

On multi-decadal timeframes, GH gas forcing and the PDO / AMO combination have been having fairly even in their relative forcing over the past century, but the GH gas forcing is growing so large that it now dominating these longer - term natural variations... so the kicker is that the rapidly increasing GH gases, now at their highest levels in millions of years, are very likely influencing the nature of ENSO, PDO, AMO, and other formerly «natural» cycles.

«The temperature variations read in the past century could be part of a larger process that is alien to humanity.»

In this new paper they write: «The most striking features in the reconstruction are the warm temperatures from ∼ 1050 to ∼ 1300 AD compared to the preceding and following centuries, the persistent cooler temperatures from ∼ 1400 to ∼ 1800 AD, and the subsequent rise to warmer temperatures which eventually seem to exceed in the last decades of the 20th century the range of past variatioIn this new paper they write: «The most striking features in the reconstruction are the warm temperatures from ∼ 1050 to ∼ 1300 AD compared to the preceding and following centuries, the persistent cooler temperatures from ∼ 1400 to ∼ 1800 AD, and the subsequent rise to warmer temperatures which eventually seem to exceed in the last decades of the 20th century the range of past variatioin the reconstruction are the warm temperatures from ∼ 1050 to ∼ 1300 AD compared to the preceding and following centuries, the persistent cooler temperatures from ∼ 1400 to ∼ 1800 AD, and the subsequent rise to warmer temperatures which eventually seem to exceed in the last decades of the 20th century the range of past variatioin the last decades of the 20th century the range of past variation.

Although the I.P.C.C. allowed for the possibility that variations in sunlight could have ended the «Little Ice Age,» a period of cooling from the 14th century to about 1850, our data argues strongly that the temperature rise of the past 250 years can not be attributed to solar changes.

Even while identifying some of the observed change in climatic behaviour, such as a 0.4 C increase in surface temperature over the past century, or about 1 mm per year sea level rise in Northern Indian Ocean, or wider variation in rainfall patterns, the document notes that no firm link between the do...

Citation: Zhang, Q., W.H. Soon, S.L. Baliunas, G.W. Lockwood, B.A. Skiff and R.R. Radick, 1994; A method of determining possible brightness variations of the Sun in past centuries from observations of solar - type stars.

In the absence of an obvious amplification mechanism, evidence for strong amplification is meager, and is also apparently at odds with solar / temperature relationships over the past century and earlier outside of the cyclic variations.

Your observation that paleo records tend to miss the shorter term variations seen in instrumental records is interesting, as this weakness would lead to doubtful conclusions that past centuries saw less climate variability than we now observe (Shaun Lovejoy article in Climate Etc. in January 2013).

Even if we could assign a certain fraction of warming over the past century or so to natural variation, we still would face very large uncertainty in aerosol influences... and modelers would continue to use those vastly uncertain aerosol influences as as a «free» variable to «tune» the models.

Drought variations in the eastern part of northwest China over the past two centuries: evidence from tree rings.

In order to extend diagnoses of recent sea - ice variations beyond the past few decades, a century - scale digital dataset of Arctic sea - ice coverage has been compiled.

Indeed, Brown explained to Media Matters that Limbaugh is «wrong» to attribute recent warming to solar activity, and added that human activity is a much bigger contributor to warming in the past century than natural variation:

Although natural variations in the solar output can explain most of the temperature variations over the past centuries, it appears that global warming by heat - trapping gases, emitted by human activity, is required to explain the sharp rise in global temperatures during the 1990s.

Changes in the amount or distribution of the sunlight illuminating the Earth can produce substantial variations in our climate, and we have proxy records of its variable output over past centuries.