Development and Disintegration of Maya Political Systems in Response to Climate Change

Radley Horton,1,a Daniel Bader,1,a Yochanan Kushnir,2 Christopher Little,3 Reginald Blake,4 and Cynthia Rosenzweig5 1Columbia University Center for Climate Systems Research, New York, NY. 2Ocean and Climate Physics Department, Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY. 3Atmospheric and Environmental Research, Lexington, MA. 4Physics Department, New York City College of Technology, CUNY, Brooklyn, NY. 5Climate Impacts Group, NASA Goddard Institute for Space Studies; Center for Climate Systems Research, Columbia University Earth Institute, New York, NY

The change of extreme precipitation is assessed with the HadGEM2-AO - 5 Regional Climate Models (RCMs) chain, which is a national downscaling project undertaken cooperatively by several South Korean institutes aimed at producing regional climate change projection with fine resolution (12.5 km) around the Korean Peninsula. The downscaling domain, resolution and lateral boundary conditions are held the same among the 5 RCMs to minimize the uncertainties from model configuration. Climatological changes reveal a statistically significant increase in the mid-21st century (2046- 2070; Fut1) and the late-21st century (2076-2100; Fut2) precipitation properties related to extreme precipitation, such as precipitation intensity and average of upper 5 percentile daily precipitation, with respect to the reference period (1981-2005). Changes depending on the intensity categories also present a clear trend of decreasing light rain and increasing heavy rain. In accordance with these results, the change of 1-in-50 year maximum precipitation intensity over South Korea is estimated by the GEV method. The result suggests that the 50-year return value (RV50) will change from -32.69% to 72.7% and from -31.6% to 96.32% in Fut1 and from -31.97% to 86.25% and from -19.45% to 134.88% in Fut2 under representative concentration pathway (RCP) 4.5 and 8.5 scenarios, respectively, at the 90% confidence level. This study suggests that multi-RCMs can be used to reduce uncertainties and assess the future change of extreme precipitation more reliably. Moreover, future projection of the regional climate change contains uncertainties evoked from not only driving GCM but also RCM. Therefore, multi-GCM and multi-RCM studies are expected to provide more robust projection.

The Earth is transitioning to a state unprecedented in human history. This transition poses a challenge for predicting the future, as climate models require testing and calibration with real‐world data from high greenhouse gas climates. Despite significant progress in climate modeling, changes in the precipitation remain highly uncertain. The Paleocene‐Eocene Thermal Maximum (PETM) was the warmest period of the Cenozoic Era, and thus serves as an analog for a hydrological cycle altered by extreme greenhouse gas warming. Here, we use paleosol‐based geochemical proxies to quantify changes in mean annual precipitation (MAP) during the PETM in the Uinta Basin, Utah. We find no change in MAP during this warming event. However, paleosol mass balance results track increased translocation of carbonates, increased clay illuviation, and increased accumulation of redox‐sensitive elements. These results, along with shifts in fluvial stratigraphy, provide evidence for increased intensity and intermittency of extreme precipitation events that may be related to changes in the transport direction, seasonality, and moisture transport capability of the North American Monsoon. Surprisingly, changes in fluvial stratigraphy, clay illuviuation, and redoximorphy continued for 105–106 years after the PETM, suggesting persistent changes in precipitation intensity despite a decrease in global temperature. These findings provide further support for an intensification of the hydrological cycle during and after the PETM, provide evidence for a decoupling between mean and extreme precipitation, and indicate the importance of multi‐proxy, regional studies for understanding the complexities of climate change.

Estimates of observed long-term changes in daily precipitation globally have been limited due to availability of high-quality observations. In this study, a new gridded dataset of daily precipitation, called Rainfall Estimates on a Gridded Network (REGEN) V1–2019, was used to perform an assessment of the climatic changes in precipitation at each global land location (except Antarctica). This study investigates changes in the number of wet days (≥1 mm) and the entire distribution of daily wet- and all-day records, in addition to trends in annual and seasonal totals from daily records, between 1950 and 2016. The main finding of this study is that precipitation has intensified across a majority of land areas globally throughout the wet-day distribution. This means that when it rains, light, moderate, or heavy wet-day precipitation has become more intense across most of the globe. Widespread increases in the frequency of wet days are observed across Asia and the United States, and widespread increases in the precipitation intensity are observed across Europe and Australia. Based on a comparison of spatial pattern of changes in frequency, intensity, and the distribution of daily totals, we propose that changes in light and moderate precipitation are characterized by changes in precipitation frequency, whereas changes in extreme precipitation are primarily characterized by intensity changes. Based on the uncertainty estimates from REGEN, this study highlights all results in the context of grids with high-quality observations.

Timing of past glaciation at the Sierra de Aconquija, northwestern Argentina, and throughout the Central Andes

ABSTRACT: An irrigation model based on a modified Thornthwaite water balance was used to simulate the effects of various hypothetical climatic changes on annual irrigation demand in a humidtemperate climate. The climatic‐change scenarios consisted of combinations of changes in temperature, precipitation, and stomatal resistance of plants to transpiration. The objectives were to (1) examine the effects of long‐term changes in these components of climatic change on annual irrigation demand, and (2) identify which of these factors would cause the largest changes in annual irrigation demand.Hypothetical climatic changes that only included increases in temperature and changes in precipitation resulted in increased annual irrigation demand, even with a 20 percent increase in precipitation. The model results showed that, for the ranges of changes in temperature and precipitation used in this study, changes in irrigation demand were more sensitive to changes in temperature than to changes in precipitation. Model results also indicated that increased stomatal resistance to transpiration counteracted the effects of increases in temperature and decreases in precipitation on irrigation demand. Changes in irrigation demand were even more sensitive to changes in stomatal resistance than to changes in temperature. A large amount of uncertainty is associated with predictions of future climatic conditions; however, uncertainty associated with natural climatic variability may be larger and may mask the effects of climatic change on irrigation demand.

Lake records provide an important source of information about climate changes on submillenial to millenial timescales during the Holocene. Analyses of lake records from Europe show that there are regionally-coherent patterns of change in lake status (a qualitative index of changes in water depth, area or volume) through the Holocene, reflecting climatically-induced changes in regional water budgets. Rapid changes in lake status occur in many regions of Europe between 9500–9000, 7500–7000 and 4500–4000 yr BP This apparent synchroneity in the timing of changes, although the direction varies from region to region, indicates that the changes in lake status are driven by changes in regional water balance caused by major reorganisations of the atmospheric circulation. Modelling studies indicate that changes in precipitation are the most important cause of changes in lake behaviour across Europe, because the lake water balance in temperate humid regions is largely controlled by runoff from the catchment. Changes in winter precipitation produce a much larger change in runoff and hence in lake response, than changes during the summer growing season. Sensitivity to precipitation changes is enhanced where solar radiation receipts are high: a given change in precipitation will therefore produce a larger response in the lake water balance in southern and eastern Europe than in northern or western Europe. The sensitivity of the lake water balance to changes in precipitation is dependent on the ratio of lake area to catchment area: sensitivity increases as the ratio becomes larger. The lake area to catchment area ratio at which a lake become sensitive varies with the magnitude of the precipitation change. Lake studies have the potential to contribute significantly to documenting and explaining Holocene climate changes across Europe. Continued improvements to the existing lake data base (including improvements to the lake chronologies), coupled with the application of geostatistical and modelling techniques will be required in order to exploit these archives fully.KeywordsLake LevelPrecipitation ChangeLake StatusEuropean LakeReservoir LakeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Holocene climate changes and variability in Europe are outlined on three time scales: long-term changes throughout the period as a whole; shorter-term fluctuations at centennial to millennial scales; and events with an annual to multi-decadal duration. Human population history in Europe during the Holocene is considered in relation to this history of climatic change and variability; in particular, evidence is reviewed that may indicate that human populations responded to, and perhaps also contributed to, climatic changes. The limitations of the data sources and chronological techniques available are briefly outlined. The prevalent long-term pattern is one of relatively warmer conditions during the early to mid-Holocene, temperature subsequently declining towards its present values. Superimposed upon this pattern, however, are marked spatial patterns in the strength of the overall changes, as well as evidence that temperature seasonality varied systematically during the Holocene. No clear patterns in precipitation change emerge at the scale of Europe as a whole; long-term precipitation changes varied both between regions and between seasons. The extent to which human populations responded to these long-term changes, in particular through changes in agricultural practices or settlement patterns, is a matter of ongoing debate. At centennial to millennial scales, numerous independent palaeoclimate sensors provide evidence of variability, with some fluctuations being recorded by many different sensors. A marked cooling event at ca. 8.2 ka BP is widely recorded. Although other fluctuations correlate with less certainty between sensors, a common pattern emerges from many of these records. There is some evidence that these fluctuations may be periodic in character. Although chronological limitations generally preclude making definitive links between records of human populations and those of climatic fluctuations, there are notable coincidences between dates for archaeological events and for climatic fluctuations. In the more recent period, however, especially the last millennium, the link is quite secure between the climatic fluctuations of the ‘Mediæval Warm Period’ and ‘Little Ice Age’, and impacts upon human populations. At the shortest time scales, annual to multi-decadal events are recorded in tree rings and other records that offer annual resolution. The most striking of these events are dramatic, albeit generally short-lived, cooling events; furthermore, at least some of these events were apparently global in extent. Although the cause of these events remains a matter of debate, it seems most probable that they reflect catastrophic events of some nature that resulted in substantial quantities of material being injected into the upper atmosphere, thus reducing penetration of solar radiation for a period of years to a decade or more. Some of these events appear to be recorded in human mythology, and it is apparent that they have often coincided with major events in human history. Although much remains to be discovered, and much further research is required, it is apparent that human populations have been affected by climatic change, variability and events during the Holocene. It is also apparent that, when considered in the context of the Holocene, the twentieth century period of increase in atmospheric concentrations of carbon dioxide and other greenhouse gases, and of the onset of consequent global climatic warming, is anomalous. The predicted rate and magnitude of twenty first century global mean temperature increase will probably exceed anything experienced during the Holocene.

Impact assessment of climate change on the hydrological response of a snow and glacier melt runoff dominated Himalayan river

Characterizing precipitation seasonality and variability in the face of future uncertainty is important for a well-informed climate change adaptation strategy. Using the Colwell index of predictability and monthly normalized precipitation data from the Coupled Model Intercomparison Project Phase 5 (CMIP5) multi-model ensembles, this study identifies spatial hotspots of changes in precipitation predictability in the United States under various climate scenarios. Over the historic period (1950–2005), the recurrent pattern of precipitation is highly predictable in the East and along the coastal Northwest, and is less so in the arid Southwest. Comparing the future (2040–2095) to the historic period, larger changes in precipitation predictability are observed under Representative Concentration Pathways (RCP) 8.5 than those under RCP 4.5. Finally, there are region-specific hotspots of future changes in precipitation predictability, and these hotspots often coincide with regions of little projected change in total precipitation, with exceptions along the wetter East and parts of the drier central West. Therefore, decision-makers are advised to not rely on future total precipitation as an indicator of water resources. Changes in precipitation predictability and the subsequent changes on seasonality and variability are equally, if not more, important factors to be included in future regional environmental assessment.

Rainfall is considered the most important physical process for landslide triggering in Portugal. It is expected that changes in the precipitation regimes in the region, as a direct consequence of climate change, will have influence in the occurrence of extreme rainfall events that will be more frequently, throughout the century. The aim of this study relied on the assessment of the projected future changes in the extreme precipitation over Portugal mainland and quantifying the correlation between extreme rainfall events and landslide events through Rainfall Triggering Thresholds (RTTs). This methodology was applied for two specific locations within two Portuguese areas of great geomorphological interest. To analyze the past frequency of landslide events, we resorted to the DISASTER database. To evaluate the possible projected changes in the extreme precipitation, we used the Iberia02 dataset and the EURO-CORDEX models’ runs at a 0.11° spatial resolution. It was analyzed the models’ performance to simulate extreme values in the precipitation series. The simulated precipitation relied on RCM-GCM models’ runs, from EURO-CORDEX, and a multimodel ensemble mean. The extreme precipitation assessment relied on the values associated to the highest percentiles, and to the values associated to the RTTs’ percentiles. To evaluate the possible future changes of the precipitation series, both at the most representative percentiles and RTTs’ percentiles, a comparison was made between the simulated values from EURO-CORDEX historical runs (1971–2000) and the simulated values from EURO-CORDEX future runs (2071–2100), considering two concentration scenarios: RCP 4.5 and RCP 8.5. In the models’ performance, the multimodel ensemble mean appeared to be within the best representing models. As for the projected changes in the extreme precipitation for the end of the century, when following the RCP 4.5 scenario, most models projected an increase in the extreme values, whereas, when following the RCP 8.5 scenario, most models projected a decrease in the extreme values.

Projected changes in extreme daily precipitation linked to changes in precipitable water and vertical velocity in CMIP6 models

We use the fully coupled WRF-Chem-SMOKE model in conjunction with satellite observations to examine the impact of smoke and the response of a frontal system to smoke-induced changes in clouds and precipitation. We show that in the high CCN/low IN regime, the dynamic buffering feedback dominates because both warm rain and riming processes are suppressed by smoke. The onset of precipitation is delayed by about one day. In the high CCN/high IN regime, more snow water path (SWP) is formed to compensate for reduced rain water path (RWP), indicating the dominance of the mixed-phase cloud buffering feedback. The onset and total amount of daily precipitation over this region were only slightly affected; however, significant changes in precipitation pattern were found.

Water resource management increasingly seeks to incorporate the impacts of global climate change in the planning of future water supplies. Studies across numerous regions have documented the sensitivity of streamflow to climate change using the precipitation elasticity of streamflow, defined as the proportional change in streamflow to a change in precipitation. This study shows that calculating precipitation elasticity of streamflow without first assessing the strength of the precipitation-streamflow relationship can produce misleading and unrealistic results. For example, the Spokane river basin precipitation elasticity of streamflow is 0.90 by using annual precipitation and streamflow accumulated on a January-December calendar year basis. This indicates that a 10% change in annual precipitation would produce an annual streamflow change of 9.0%. However, using water year (Oct-Sep, in this case) precipitation and streamflow data gives an elasticity of 1.65, indicating a 10% change in annual precipitation would result in a 16.5% change in annual streamflow. Further analysis shows that the water year data has a much stronger precipitation-streamflow relationship (R 2 =0.72) compared with the calendar year data (R 2 =0.23). From this we infer that the precipitation elasticity of streamflow should be calculated using the seasonality that produces the strongest precipitation-streamflow relationship, as the precipitation elasticity of streamflow is sensitive to the strength of the precipitation-streamflow relationship. A useful practice is to use water year data series - with annual cycles starting from the beginning of the dry season or from just before the snowmelt period. The results of the temporal variations of precipitation elasticity of streamflow for 30 and 50 year blocks indicate that 50-yr-block time series generate less temporal variation, as expected given the longer time period used. These results have implications for the use of elasticity as a rule of thumb under changing climate and climate change and variability impact studies. It can be argued that it is better to use as long a record as possible to estimate elasticity as this captures the range of observed variability. However, with potential climate change and variability, there may be good reason to use only the most recent record (e.g., the most recent 30-50 years) to estimate the elasticity, or use dry or wet periods that are similar to future projections to quantify the climatic change impacts on streamflow. The relationships between the elasticity values and annual rainfall, annual streamflow, and the runoff coefficient (ratio of annual streamflow to annual precipitation) for the Murray-Darling Basin indicate that the elasticity values are generally negatively correlated to these streamflow and runoff coefficient , i.e., a low flow period in general results in a larger elasticity value. Moreover, the relationship between elasticity and the runoff coefficient is stronger than that between elasticity and rainfall, with correlation coefficients of - 0.423 and 0.089 respectively. The relationship between elasticity and streamflow is in-between at -0.260. This implies that annual rainfall is not the only driving force causing larger elasticities in recent years. These research results can be used to guide the application of elasticity methods to quantify hydrological responses to climatic change that inform long-term water management strategies.

Global warming can profoundly influence the mean climate over the Arabian Peninsula, which may significantly influence both natural and human systems. The present study aims to investigate the changes in the precipitation regime in response to climate change over the Arabian Peninsula, with special emphasis on the United Arab Emirates (UAE). This work is performed using a sub-set of high-resolution NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) data derived from Coupled Model Intercomparison Project Phase 6 (CMIP6) Global Climate Models under three different Shared Socioeconomic Pathway (SSP) scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5). The changes are analyzed in three phases such as 2021–2050 (near future), 2051–2080 (mid future) and 2080–2100 (far future), with the period of 1985–2014 as the baseline. This study represents the first attempt to utilize data from NEX-GDDP models to project the regional patterns of precipitation regime across the Arabian Peninsula. Results suggest that the annual precipitation is expected to increase over most of the UAE by up to 30%, particularly intense from the mid-future onwards in all scenarios. Specifically, the spatiotemporal distribution of precipitation extremes such as intensity, 1-day highest precipitation, and precipitation exceeding 10 mm days are increasing; in contrast, the consecutive dry days may decrease towards the end of the century. The results show that the changes in extreme precipitation under a warming scenario relative to the historical period indicate progressive wetting across UAE, accompanied by increased heavy precipitation events and reduced dry spell events, particularly under the high emission scenarios. A high-resolution dataset is essential for a better understanding of changes in precipitation patterns, especially in regions where more detailed information is needed on a local scale to achieve water, food security, and environmental sustainability to formulate effective adaptation strategies for mitigating the potential risks and consequences associated with variations in wet and dry conditions.