Recent global warming hiatus was caused by Northern Hemisphere winter cooling 1999-2008. Scientists say better understanding of timing methods would shed new light on mechanisms of recent global warming hiatus- AGU peer reviewed study, July 14, 2015

7/14/15, "The recent hiatus in global warming of the land surface: scale-dependent breakpoint occurrences in space and time," GRL, AGU, Lingxaio Ying, Shilong Piao 

"Abstract"

"The spatial and temporal variability of the recent land warming hiatus have seldom been explored, despite their importance for understanding the mechanisms underlying the phenomenon. In this study, we applied piecewise linear regression to investigate the spatiotemporal patterns of the breakpoint time of warming over 40 years (1974–2013). Our results showed that at the global scale, mean annual temperature (MAT) over the land increased significantly until 2005 and that the warming trend then stalled. However, the breakpoint time of the warming varied greatly among different seasons and continents.

We found no statistically significant breakpoint in MAT over the Northern Hemisphere, but MAT over the Southern Hemisphere showed a significant breakpoint (P (less than) 0.001) in 1979. At the seasonal scale, only the winter season (Dec–Jan–Feb) showed a statistically significant breakpoint in global land temperature. The other seasons showed continuous increasing temperature during the whole study period. Our study examined the recent global warming hiatus on the land surface using an area-weighted summary of a scale-dependent phenomenon with substantial spatiotemporal heterogeneity, and revealed the winter cooling in the Northern Hemisphere low-mid latitudes in 1999-2008 as the major contributor to the global warming hiatus on land surface in 2005. This result highlights the importance of using a statistical method to identify the timing of climate phase change. A better understanding of the processes behind the spatiotemporal patterns of local-scale breakpoint occurrences in land surface temperature would shed new light on the mechanisms of the recent global warming hiatus." via Hockey Schtick


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Added:

July 2014 PNAS study also found that "global climate change" isn't global after all, Northern and Southern Hemispheres operate differently, and it's not even a matter of one leads or lags. Every scientist and every politician knows this. Why wouldn't a single one scream into a microphone that a UN Global Climate Treaty based only on global CO2 can't possibly help global climate and must be called off? Peer reviewed science says, "a generalised global approach isn't the solution." Precious taxpayer dollars that could help the poor and needy go instead to the global elite:

8/4/14, "Climate change not so global," University of Queensland, Australia

"Scientists are calling for a better understanding of regional climates, after research into New Zealand's glaciers has revealed climate change in the Northern Hemisphere does not directly affect the climate in the Southern Hemisphere.

The University of Queensland study showed that future climate changes may impact differently in the two hemispheres, meaning a generalised global approach isn’t the solution to climate issues.

UQ School of Geography, Planning and Environmental Management Head Professor Jamie Shulmeister said the study provided evidence for the late survival of significant glaciers in the mountains of New Zealand at the end of the last ice age – a time when other ice areas were retreating..

“This study reverses previous findings which suggested that New Zealand's glaciers disappeared at the same time as ice in the Northern Hemisphere,” he said.

“We showed that when the Northern Hemisphere started to warm at the end of the last ice age, New Zealand glaciers were unaffected.

“These glaciers began to retreat several thousand years later, when changes in the Southern Ocean led to increased carbon dioxide emissions and warming.

”This indicates that future climate change may impact differently in the two hemispheres and that changes in the Southern Ocean are likely to be critical for Australia and New Zealand.”

The study used exposure dating of moraines - mounds of rocks formed by glaciers - to reconstruct the rate of ice retreat in New Zealand’s Ashburton Valley after the last glacial maximum – the time when the ice sheets were at their largest.

The researchers found that the period from the last glacial maximum to the end of the ice age was longer in New Zealand than in the Northern Hemisphere.

They also found that the maximum glacier extent in New Zealand occurred several thousand years before the maximum in the Northern Hemisphere, demonstrating that growth of the northern ice sheets did not cause expansion of New Zealand glaciers.

“New Zealand glaciers responded largely to local changes in the Southern Ocean, rather than changes in the Northern Hemisphere as was previously believed,” Professor Shulmeister said.

“This study highlights the need to understand regional climate rather than a global one-size-fits-all.”

The research was conducted in collaboration with the University of Griefswald, Germany, the Australian Nuclear Science and Technology Organisation, and the University of Canterbury, New Zealand, and published in the Proceedings of the National Academy of Science in July."
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PNAS peer reviewed study cited above:

7/28/2014, "The early rise and late demise of New Zealand’s last glacial maximum," PNAS.org

1. Henrik Rother^a,¹,
2. David Fink^b,
3. James Shulmeister^c,
4. Charles Mifsud^b,
5. Michael Evans^d, and
6. Jeremy Pugh^e,²

"Significance"...

"This record from a key site in the midlatitude Southern Hemisphere shows that the largest glacial advance did not coincide with the coldest temperatures during this phase. We also show that the regional post-LGM ice retreat was very gradual, contrary to the rapid ice collapse widely inferred. This demonstrates that glacial records from New Zealand are neither synchronous with nor simply lag or lead Northern Hemisphere ice sheet records, which has important implications for the reconstruction of past interhemispheric climate linkages and mechanisms.".

"Abstract"

"Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the last glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models....These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early last glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka."

"This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1401547111/-/DCSupplemental." 




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