2110 Years Of Wet and Dry Spells in Europe And Beyond

2110 Years Of Climate History From Tree Rings

A new study uses tree rings to example European droughts and wet spells over the last 2110 years, showing that Europe's dry spell from 2015-2018 was a 2110+ year record drought. 

Over the 2,110-year period, the tree-ring isotope data showed there were very wet summers, such as 200, 720 and 1100 CE, and very dry summers, such as 40, 590, 950 and 1510 CE. Despite these "out of the ordinary years", the results show that for the past two millennia, Europe has been slowly getting drier. The samples from 2015-2018, however, show that drought conditions in recent summers far exceed anything in the 2,110 years.

Via Science Daily.

The current record drought in Europe could be older. But the tree ring data doesn't go back further.

Older Paleoclimate Events

We know from other data that there was a major droughts or climate events in Europe ca. 1200 BCE (possibly linked to a volcanic eruption in Iceland that took place in 1159 BCE).

There were also droughts in Europe around 2200 BCE in Europe and the "Iron Age Cold Event" around 800 BCE, in events called Bond Events. 

The Iron Age Cold Epoch (also referred to as Iron Age climate pessimum or Iron Age neoglaciation) was a period of unusually cold climate in the North Atlantic region, lasting from about 900 BC to about 300 BC, with an especially cold wave in 450 BC during the expansion of ancient Greece. It was followed by the Roman Warm Period (250 BC – 400 AD).

From Wikipedia. 

Bond Events are also known at around 3900 BCE (following which the Sahara Desert reforms by 3500-3000 BCE and close to the beginning of the Bronze Age) and 6200 BCE.  

See generally, my March 2, 2014 post entitled "The Holocene Climate Events That Shaped Prehistory and Ancient History" at this blog, discussing the 8.2 kiloyear event, the 5.9 kiloyear event and the 4.1 kiloyear event, and possibly less severe event which helped to precipitate the historical events known as Bronze Age Collapse about 3.2 thousand years ago, while referencing other posts on the topic including more ancient climate data.

Other Notable Papers Referenced In This Paper

A few referenced paper in the study are also worth mentioning. Their abstracts and citations are as follows:

The second plague pandemic in medieval Europe started with the Black Death epidemic of 1347–1353 and killed millions of people over a time span of four centuries. It is commonly thought that after its initial introduction from Asia, the disease persisted in Europe in rodent reservoirs until it eventually disappeared. 

Here, we show that climate-driven outbreaks of Yersinia pestis in Asian rodent plague reservoirs are significantly associated with new waves of plague arriving into Europe through its maritime trade network with Asia. This association strongly suggests that the bacterium was continuously reimported into Europe during the second plague pandemic, and offers an alternative explanation to putative European rodent reservoirs for how the disease could have persisted in Europe for so long.

Schmid, B. V. et al. "Climate-driven introduction of the Black Death and successive plague reintroductions into Europe." Proc. Natl Acad. Sci. USA 112, 3020–3025 (2015).

Climate variations influenced the agricultural productivity, health risk, and conflict level of preindustrial societies. Discrimination between environmental and anthropogenic impacts on past civilizations, however, remains difficult because of the paucity of high-resolution paleoclimatic evidence. We present tree ring–based reconstructions of central European summer precipitation and temperature variability over the past 2500 years. Recent warming is unprecedented, but modern hydroclimatic variations may have at times been exceeded in magnitude and duration. Wet and warm summers occurred during periods of Roman and medieval prosperity. Increased climate variability from ~250 to 600 C.E. coincided with the demise of the western Roman Empire and the turmoil of the Migration Period. Such historical data may provide a basis for counteracting the recent political and fiscal reluctance to mitigate projected climate change.

Büntgen, U. et al., "2500 years of European climate variability and human susceptibility." 331 Science 578–582 (2011).

Climatic changes during the first half of the Common Era have been suggested to play a role in societal reorganizations in Europe and Asia. In particular, the sixth century coincides with rising and falling civilizations, pandemics, human migration and political turmoil. Our understanding of the magnitude and spatial extent as well as the possible causes and concurrences of climate change during this period is, however, still limited. 

Here we use tree-ring chronologies from the Russian Altai and European Alps to reconstruct summer temperatures over the past two millennia. We find an unprecedented, long-lasting and spatially synchronized cooling following a cluster of large volcanic eruptions in 536, 540 and 547 AD, which was probably sustained by ocean and sea-ice feedbacks, as well as a solar minimum. 

We thus identify the interval from 536 to about 660 AD as the Late Antique Little Ice Age. Spanning most of the Northern Hemisphere, we suggest that this cold phase be considered as an additional environmental factor contributing to the establishment of the Justinian plague, transformation of the eastern Roman Empire and collapse of the Sasanian Empire, movements out of the Asian steppe and Arabian Peninsula, spread of Slavic-speaking peoples and political upheavals in China.

Büntgen, U. et al. "Cooling and societal change during the Late Antique Little Ice Age from 536 to around 660 AD." Nat. Geosci. 9, 231–236 (2016).

The Mongol invasion of Eastern Europe and especially its sudden withdrawal from Hungary in 1242 CE, has generated much speculation and an array of controversial theories. None of them, however, considered multifaceted environmental drivers and the coupled analysis of historical reports and natural archives. Here we investigate annually resolved, absolutely dated and spatially explicit paleoclimatic evidence between 1230 and 1250 CE. Documentary sources and tree-ring chronologies reveal warm and dry summers from 1238–1241, followed by cold and wet conditions in early-1242. Marshy terrain across the Hungarian plain most likely reduced pastureland and decreased mobility, as well as the military effectiveness of the Mongol cavalry, while despoliation and depopulation ostensibly contributed to widespread famine. These circumstances arguably contributed to the determination of the Mongols to abandon Hungary and return to Russia. While overcoming deterministic and reductionist arguments, our ‘environmental hypothesis’ demonstrates the importance of minor climatic fluctuations on major historical events.

Büntgen, U. & Di Cosmo, N. "Climatic and environmental aspects of the Mongol withdrawal from Hungary in 1242 CE." Sci. Rep. 6, 25606 (2016) (open access).

The spatial context is critical when assessing present-day climate anomalies, attributing them to potential forcings and making statements regarding their frequency and severity in a long-term perspective. Recent international initiatives have expanded the number of high-quality proxy-records and developed new statistical reconstruction methods. These advances allow more rigorous regional past temperature reconstructions and, in turn, the possibility of evaluating climate models on policy-relevant, spatio-temporal scales. 

Here we provide a new proxy-based, annually-resolved, spatial reconstruction of the European summer (June–August) temperature fields back to 755 CE based on Bayesian hierarchical modelling (BHM), together with estimates of the European mean temperature variation since 138 BCE based on BHM and composite-plus-scaling (CPS). Our reconstructions compare well with independent instrumental and proxy-based temperature estimates, but suggest a larger amplitude in summer temperature variability than previously reported. Both CPS and BHM reconstructions indicate that the mean 20th century European summer temperature was not significantly different from some earlier centuries, including the 1st, 2nd, 8th and 10th centuries CE. The 1st century (in BHM also the 10th century) may even have been slightly warmer than the 20th century, but the difference is not statistically significant. Comparing each 50 yr period with the 1951–2000 period reveals a similar pattern. Recent summers, however, have been unusually warm in the context of the last two millennia and there are no 30 yr periods in either reconstruction that exceed the mean average European summer temperature of the last 3 decades (1986–2015 CE). A comparison with an ensemble of climate model simulations suggests that the reconstructed European summer temperature variability over the period 850–2000 CE reflects changes in both internal variability and external forcing on multi-decadal time-scales. For pan-European temperatures we find slightly better agreement between the reconstruction and the model simulations with high-end estimates for total solar irradiance. Temperature differences between the medieval period, the recent period and the Little Ice Age are larger in the reconstructions than the simulations. This may indicate inflated variability of the reconstructions, a lack of sensitivity and processes to changes in external forcing on the simulated European climate and/or an underestimation of internal variability on centennial and longer time scales.

Luterbacher, J. et al. "European summer temperatures since Roman times." 11 Environ. Res. Lett. 024001 (2016).

A 5-year-resolution absolute-dated oxygen isotope record from Dongge Cave, southern China, provides a continuous history of the Asian monsoon over the past 9000 years. Although the record broadly follows summer insolation, it is punctuated by eight weak monsoon events lasting ∼1 to 5 centuries. One correlates with the “8200-year” event, another with the collapse of the Chinese Neolithic culture, and most with North Atlantic ice-rafting events. Cross-correlation of the decadal- to centennial-scale monsoon record with the atmospheric carbon-14 record shows that some, but not all, of the monsoon variability at these frequencies results from changes in solar output.

Wang, Y. et al. "The Holocene Asian monsoon: links to solar changes and North Atlantic climate." 308 Science 854–857 (2005).

The lack of a precisely-dated, unequivocal climate proxy from northern China, where precipitation variability is traditionally considered as an East Asian summer monsoon (EASM) indicator, impedes our understanding of the behaviour and dynamics of the EASM. 

Here we present a well-dated, pollen-based, ~20-yr-resolution quantitative precipitation reconstruction (derived using a transfer function) from an alpine lake in North China, which provides for the first time a direct record of EASM evolution since 14.7 ka (ka = thousands of years before present, where the “present” is defined as the year AD 1950). 

Our record reveals a gradually intensifying monsoon from 14.7–7.0 ka, a maximum monsoon (30% higher precipitation than present) from ~7.8–5.3 ka and a rapid decline since ~3.3 ka. These insolation-driven EASM trends were punctuated by two millennial-scale weakening events which occurred synchronously to the cold Younger Dryas and at ~9.5–8.5 ka and by two centennial-scale intervals of enhanced (weakened) monsoon during the Medieval Warm Period (Little Ice Age). Our precipitation reconstruction, consistent with temperature changes but quite different from the prevailing view of EASM evolution, points to strong internal feedback processes driving the EASM and may aid our understanding of future monsoon behaviour under ongoing anthropogenic climate change.

Chen, F. et al. "East Asian summer monsoon precipitation variability since the last deglaciation." 5 Sci. Rep. 11186 (2015) (open access).

Oxygen isotope records from Chinese caves characterize changes in both the Asian monsoon and global climate. Here, using our new speleothem data, we extend the Chinese record to cover the full uranium/thorium dating range, that is, the past 640,000 years. The record’s length and temporal precision allow us to test the idea that insolation changes caused by the Earth’s precession drove the terminations of each of the last seven ice ages as well as the millennia-long intervals of reduced monsoon rainfall associated with each of the terminations. On the basis of our record’s timing, the terminations are separated by four or five precession cycles, supporting the idea that the ‘100,000-year’ ice age cycle is an average of discrete numbers of precession cycles. Furthermore, the suborbital component of monsoon rainfall variability exhibits power in both the precession and obliquity bands, and is nearly in anti-phase with summer boreal insolation. These observations indicate that insolation, in part, sets the pace of the occurrence of millennial-scale events, including those associated with terminations and ‘unfinished terminations’.

Cheng, H. et al. "The Asian monsoon over the past 640,000 years and ice age terminations." 534 Nature 640–646 (2016).

The latitudinal temperature gradient between the Equator and the poles influences atmospheric stability, the strength of the jet stream and extratropical cyclones. 

Recent global warming is weakening the annual surface gradient in the Northern Hemisphere by preferentially warming the high latitudes; however, the implications of these changes for mid-latitude climate remain uncertain. Here we show that a weaker latitudinal temperature gradient—that is, warming of the Arctic with respect to the Equator—during the early to middle part of the Holocene coincided with substantial decreases in mid-latitude net precipitation (precipitation minus evapotranspiration, at 30° N to 50° N). 

We quantify the evolution of the gradient and of mid-latitude moisture both in a new compilation of Holocene palaeoclimate records spanning from 10° S to 90° N and in an ensemble of mid-Holocene climate model simulations. The observed pattern is consistent with the hypothesis that a weaker temperature gradient led to weaker mid-latitude westerly flow, weaker cyclones and decreased net terrestrial mid-latitude precipitation. 

Currently, the northern high latitudes are warming at rates nearly double the global average, decreasing the Equator-to-pole temperature gradient to values comparable with those in the early to middle Holocene. If the patterns observed during the Holocene hold for current anthropogenically forced warming, the weaker latitudinal temperature gradient will lead to considerable reductions in mid-latitude water resources.

Routson, C. C. et al. "Mid-latitude net precipitation decreased with Arctic warming during the Holocene." 568 Nature 83–87 (2019).

The injection of sulfur into the stratosphere by explosive volcanic eruptions is the cause of significant climate variability. Based on sulfate records from a suite of ice cores from Greenland and Antarctica, the eVolv2k database includes estimates of the magnitudes and approximate source latitudes of major volcanic stratospheric sulfur injection (VSSI) events from 500 BCE to 1900 CE, constituting an update of prior reconstructions and an extension of the record by 1000 years. 

The database incorporates improvements to the ice core records (in terms of synchronisation and dating) and refinements to the methods used to estimate VSSI from ice core records, and it includes first estimates of the random uncertainties in VSSI values. 

VSSI estimates for many of the largest eruptions, including Samalas (1257), Tambora (1815), and Laki (1783), are within 10 % of prior estimates. 

A number of strong events are included in eVolv2k which are largely underestimated or not included in earlier VSSI reconstructions, including events in 540, 574, 682, and 1108 CE. 

The long-term annual mean VSSI from major volcanic eruptions is estimated to be  ∼ 0.5 Tg [S] yr−1,  ∼ 50 % greater than a prior reconstruction due to the identification of more events and an increase in the magnitude of many intermediate events. A long-term latitudinally and monthly resolved stratospheric aerosol optical depth (SAOD) time series is reconstructed from the eVolv2k VSSI estimates, and the resulting global mean SAOD is found to be similar (within 33 %) to a prior reconstruction for most of the largest eruptions. The long-term (500 BCE–1900 CE) average global mean SAOD estimated from the eVolv2k VSSI estimates including a constant background injection of stratospheric sulfur is  ∼ 0.014, 30 % greater than a prior reconstruction. 

These new long-term reconstructions of past VSSI and SAOD variability give context to recent volcanic forcing, suggesting that the 20th century was a period of somewhat weaker than average volcanic forcing, with current best estimates of 20th century mean VSSI and SAOD values being 25 and 14 % less, respectively, than the mean of the 500 BCE to 1900 CE period. The reconstructed VSSI and SAOD data are available at https://doi.org/10.1594/WDCC/eVolv2k_v2.

Toohey, M. & Sigl, M. "Volcanic stratospheric sulfur injections and aerosol optical depth from 500 BCE to 1900 CE." 9 Earth Syst. Sci. Data 809–831 (2017).