Global warming has slowed - and recent changes are down to ‘natural variability’

[Jesse]

Source: Daily Mail

Global warming hasn't happened as fast as expected, according to a new study based on 1,000 years of temperature records.

The research claims that natural variability in surface temperatures over the course of a decade can account for increases and dips in warming rates.

But it adds that these so-called 'climate wiggles' could also, in the future, cause our planet to warm up much faster than anticipated.

The study compared its results to the most severe emissions scenarios outlined by the Intergovernmental Panel on Climate Change (IPCC).

'Based on our analysis, a middle-of-the-road warming scenario is more likely, at least for now,' said Patrick Brown, a doctoral student in climatology at Duke University. 'But this could change.'

The Duke-led study says that variability is caused by interactions between the ocean and atmosphere, and other natural factors.

They claim these 'wiggles' can slow or speed the rate of warming from decade to decade, and exaggerate or offset the effects of increases in greenhouse gas concentrations.

If not properly explained and accounted for, they may skew the reliability of climate models and lead to over-interpretation of short-term temperature trends.

The research, uses observed data, rather than the more commonly used climate models, to estimate decade-to-decade variability.

'At any given time, we could start warming at a faster rate if greenhouse gas concentrations in the atmosphere increase without any offsetting changes in aerosol concentrations or natural variability,' said Wenhong Li, assistant professor of climate at Duke, who conducted the study with Brown.

The team examined whether climate models, such as those used by the IPCC, accurately account for natural chaotic variability that can occur in the rate of global warming.

To test these, created a new statistical model based on reconstructed empirical records of surface temperatures over the last 1,000 years.

'By comparing our model against theirs, we found that climate models largely get the 'big picture' right but seem to underestimate the magnitude of natural decade-to-decade climate wiggles,' Brown said.

'Our model shows these wiggles can be big enough that they could have accounted for a reasonable portion of the accelerated warming we experienced from 1975 to 2000, as well as the reduced rate in warming that occurred from 2002 to 2013.'

'Statistically, it's pretty unlikely that an 11-year hiatus in warming, like the one we saw at the start of this century, would occur if the underlying human-caused warming was progressing at a rate as fast as the most severe IPCC projections,' Brown said.

'Hiatus periods of 11 years or longer are more likely to occur under a middle-of-the-road scenario.'

Under the IPCC's middle-of-the-road scenario, there was a 70 per cent likelihood that at least one hiatus lasting 11 years or longer would occur between 1993 and 2050, Brown said.

'That matches up well with what we're seeing.'

There's no guarantee, however, that this rate of warming will remain steady in coming years, Li stressed.

'Our analysis clearly shows that we shouldn't expect the observed rates of warming to be constant. They can and do change.'


Source

© Copyright Original Source

Using observed data in science? What kind of witchcraft is this?

[Paprika]

The research, uses observed data, rather than the more commonly used climate models, to estimate decade-to-decade variability.
...
Using observed data in science? What kind of witchcraft is this?

What is lacking, of course, is to make skillful predictions to test the model against future data.

[Jesse]

What is lacking, of course, is to make skillful predictions to test the model against future data.

"Skillfull predictions" seem...oxymoronic to me in this instance. Considering they didn't accounted for The Attack of the Wiggles here. I have a prediction, the climate will continue to go up and down in temperature for the foreseeable future. Now give me a grant.

[Paprika]

"Skillfull predictions" seem...oxymoronic to me in this instance.

Right, but I think you get what I mean. An extreme example would be 'this coin when flipped will either land heads or tails' which will almost always be true.

Which means, of course, that making a very wide range of claims is a great way to prevent one's model from being falsified since one has covered the likely range of possibilities.

[Leonhard]

Using observed data in science? What kind of witchcraft is this?

Ah yes... because apparently the modern science on global warming is free of data? This reeks of stale cod.

*Leonhard puts on his sleuth fedora and trenchcoat and goes to investigate*

Aha, this has already been posted up in Civics, only the Daily Mail (being a tabloid) make fairly ridiculous claims compared to the news article that seer posted.

This has nothing to do about using data, this has something to do about comparing various simulations against reconstructed temperature profiles, in order to see whether the current rise and "flatlining" were inconsistent with some of the models from the IPCC.

We already know that its utterly inconsistent with no rise at all, and this is not contested. The IPCC had several models of how the temperature might rise, based on various unknowns, such as industry developments, and feedback from the environment such a melting tundra releasing huge amounts of methane. The worst model predicts about 9F rise by the end of this century, the weakest (which assumes China and India significantly reduces their CO2 output by 2050) predicts about 2.7F (numbers are from memory).

Why the need to compare these models against the average temperature record?

The average temperature goes up and down goes like the stock market, with a trend. There are some random fluctuations. It comes mainly from the fact that we're not capable of telling the temperature of every single mile of air in the world, but only various selected spots who are susceptible to the randomness of local weather. The total average is also susceptible dynamics between the atmosphere and the ocean (the temperature of which we have fairly bad grasp of. In some circumstances, a hot atmosphere will heat up the ocean from the bottom up, rather than the top down!). It averages out, but there's still some noise left. So you have to look at trends over three decades, which is what they did.

And they found that the data might be inconsistent with the worst of the models. Which is good, because that one was awful. They said it was perfectly consistent with the mid-range models, and in their report they even clearly stated that this would not constitute evidence that warming had somehow stopped.

[Jesse]

Aha, this has already been posted up in Civics, only the Daily Mail (being a tabloid) make fairly ridiculous claims compared to the news article that seer posted.

Since I didn't see it, I had no idea Seer already posted this information. Sorry Seer, I didn't mean to post this after you.

[HMS_Beagle]

Using observed data in science? What kind of witchcraft is this?

It's the usual hatchet job by the Daily Mail. All this study did is look at the short term natural variability of temperature - the "noise" in the long term signal. It doesn't cast the slightest doubt at all on the long term rising trend which is still easily discernible through the noise. It also doesn't cast the slightest doubt humans are responsible for the large majority of the temperature rise in the last 100+ years.

[shunyadragon]

Global warming hasn't happened as fast as expected, according to a new study based on 1,000 years of temperature records.

Not correct based on how scientists view the recent climate change in past one hundred years.

Source: Daily Mail

The research claims that natural variability in surface temperatures over the course of a decade can account for increases and dips in warming rates.

But it adds that these so-called 'climate wiggles' could also, in the future, cause our planet to warm up much faster than anticipated.

The study compared its results to the most severe emissions scenarios outlined by the Intergovernmental Panel on Climate Change (IPCC).

'Based on our analysis, a middle-of-the-road warming scenario is more likely, at least for now,' said Patrick Brown, a doctoral student in climatology at Duke University. 'But this could change.'

The Duke-led study says that variability is caused by interactions between the ocean and atmosphere, and other natural factors.

They claim these 'wiggles' can slow or speed the rate of warming from decade to decade, and exaggerate or offset the effects of increases in greenhouse gas concentrations.

If not properly explained and accounted for, they may skew the reliability of climate models and lead to over-interpretation of short-term temperature trends.

The research, uses observed data, rather than the more commonly used climate models, to estimate decade-to-decade variability.

'At any given time, we could start warming at a faster rate if greenhouse gas concentrations in the atmosphere increase without any offsetting changes in aerosol concentrations or natural variability,' said Wenhong Li, assistant professor of climate at Duke, who conducted the study with Brown.

The team examined whether climate models, such as those used by the IPCC, accurately account for natural chaotic variability that can occur in the rate of global warming.

To test these, created a new statistical model based on reconstructed empirical records of surface temperatures over the last 1,000 years.

'By comparing our model against theirs, we found that climate models largely get the 'big picture' right but seem to underestimate the magnitude of natural decade-to-decade climate wiggles,' Brown said.

'Our model shows these wiggles can be big enough that they could have accounted for a reasonable portion of the accelerated warming we experienced from 1975 to 2000, as well as the reduced rate in warming that occurred from 2002 to 2013.'

'Statistically, it's pretty unlikely that an 11-year hiatus in warming, like the one we saw at the start of this century, would occur if the underlying human-caused warming was progressing at a rate as fast as the most severe IPCC projections,' Brown said.

'Hiatus periods of 11 years or longer are more likely to occur under a middle-of-the-road scenario.'

Under the IPCC's middle-of-the-road scenario, there was a 70 per cent likelihood that at least one hiatus lasting 11 years or longer would occur between 1993 and 2050, Brown said.

'That matches up well with what we're seeing.'

There's no guarantee, however, that this rate of warming will remain steady in coming years, Li stressed.

'Our analysis clearly shows that we shouldn't expect the observed rates of warming to be constant. They can and do change.'


Source

© Copyright Original Source

Using observed data in science? What kind of witchcraft is this?

Not witchcraft, just another interpretation of the data available. This is possible, but I do not agree with this analysis. In the past I considered this view very possible, but in the analysis of the recent data, past one hundred years compared to the cycles of the past several thousand, I do not consider the trend of the past onehundred years to fit a normal pattern.

I would review this in more detail and comment more later.