Our Common Future Under Climate Change

International Scientific Conference 7-10 JULY 2015 Paris, France

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Wednesday 8 July - 15:00-16:30 UPMC Jussieu - Amphi Herpin

2201 - Between the cracks of future climate projections: exploring weather events and climate scenarios with no precedence

Parallel Session

Lead Convener(s): B. Van Den Hurk (KNMI, De Bilt, Netherlands)

Convener(s): Z. Mark (James Cook University, Townsville, Australia), D.A. Stainforth (London School of Economics, London, United Kingdom), S. Turton (James Cook University, Cairns, Australia), F. Berkhout (King's College London, London, United Kingdom)

Tales of Future Weather

W. Hazeleger (KNMI, De Bilt, Netherlands), W. Hazeleger (Netherlands eScience Center/KNMI/WU, Amsterdam, Netherlands)

Abstract details
Tales of Future Weather

W. Hazeleger (1)
(1) Netherlands eScience Center/KNMI/WU, Amsterdam, Netherlands

Abstract content

Society is vulnerable to extreme weather events and, by extension, to human impacts on future events. As climate changes weather patterns will change. The search is on for more effective methodologies to aid decision-makers both in mitigation to avoid climate change and in adaptation to changes. The traditional approach uses ensembles of climate model simulations, statistical bias correction, downscaling to the spatial and temporal scales relevant to decision-makers, and then translation into quantities of interest. The veracity of this approach cannot be tested, and it faces in-principle challenges. Predictability beyond 'weather' time scales is limited and physical consistency is often lost when downscaling. Alternatively, numerical weather prediction models in a hypothetical climate setting can provide tailored narratives for high-resolution simulations of high-impact weather in a future climate. This 'Tales of Future Weather' approach will aid in the interpretation of lower-resolution simulations such as produced in the Coupled Model Intercomparison Projects (CMIP).  At this presentation a number of real-world cases will be presented where vulnerability to meteorological conditions was exposed. These are typically high-impact, not necessarily extreme, weather events. For instance compounded events of storm surges and extreme rainfall in the midlatitudes and of heat and drought in the subtropics. We will show how narratives of those analogues can describe the events in an alternative climatic setting to aid decision-makers. Producing the narratives is a transdisciplinary process where scientistis and decision makers co-develop the information needed.  Arguably, 'Tales' potentially provides complementary, more realistic and more physically consistent pictures of what future weather might look like.

No-analogue Climate Futures in the Tropics

R. Corlett (Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan, China)

Abstract details
No-analogue Climate Futures in the Tropics

R. Corlett (1)
(1) Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Center for integrative conservation, Menglun, Mengla, Yunnan, China

Abstract content

Climatic extremes in the tropics—cyclones, floods, droughts, and heatwaves—currently kill tens of thousands of people a year, and damage or destroy the livelihoods of many others. Wild species are presumably adapted to these extremes and, although individuals are killed, their populations usually persist, except when natural weather extremes interact with land-use change and other human impacts to change fire regimes and exacerbate floods and droughts.  Climate models predict a further 1-2oC warming by 2050 and 1-4oC by 2100 for the tropics, but trends in rainfall and other variables vary between models for most regions. In much of the lowland tropics, this warming will create climates for which there is no existing analogue anywhere on Earth.  Moreover, the low variability of tropical temperatures means that a rise in mean temperature of 2-3oC will bring routine maxima as high as today’s extremes and new extremes that are higher than any that occur today. Although less certain, there are also good reasons for expecting increases in other climate extremes, including floods, droughts, and high-intensity cyclones. Predicting the responses of both human and natural systems to novel climate extremes is inherently difficult. Human societies have a considerable capacity to adjust to change, but exposure to climate change is likely to be greatest and adaptive capacity least among the poorest and most marginalized people. Predictions for natural systems depend on models, but we currently lack the data needed to assess their reliability when extrapolated beyond current conditions.  There is an urgent need for both better models, built on a mechanistic understanding of the processes involved, and large-scale experiments.

Future projection of precipitation associated with Cutoff Lows over South Africa in a Coupled Global Climate Model

A. Favre (Université de Bourgogne, Dijon, France), C. Lennard (University of Cape Town, Cape Town, South Africa), B. Hewitson (University of Cape Town, Rondebosch, South Africa), Y. Richard (Université de Bourgogne, Dijon, France)

Abstract details
Future projection of precipitation associated with Cutoff Lows over South Africa in a Coupled Global Climate Model

A. Favre (1) ; C. Lennard (2) ; B. Hewitson (3) ; Y. Richard (1)
(1) Université de Bourgogne, Centre de recherches de climatologie, umr 6282 biogéosciences cnrs, Dijon, France; (2) University of Cape Town, Climate System Analysis Group, Cape Town, South Africa; (3) University of Cape Town, Environmental and Geographical Science, Rondebosch, South Africa

Abstract content

In South Africa, Cut-off Lows (CoLs) are known to be responsible for tempestuous weather and some remarkable precipitation events. This work presents how precipitation associated with CoLs may evolve in the region of South Africa in a context of global warming. Using the historical (1976-2005) and the Representative Concentration Pathway 8.5 (RCP8.5, 2006-2100) simulations of the Centre National de Recherches Météorologiques coupled global climate model (CNRM-CM5), the trajectories of 500-hPa CoLs have been constructed following the methodology presented in Favre et al 2013. During the historical period, we find that the geographical and seasonal distributions of CoLs’ frequency over South Africa and surrounding oceans are well simulated by the CNRM-CM5. In addition, the main observed features of precipitation associated with CoLs are correctly reproduced by the model. According to the RCP8.5 simulation, drier conditions are projected over South Africa by the end of the 21st century and the CNRM-CM5 also presents a general decrease in annual precipitation, except over the plateau in the Northern Cape province. Precipitation associated with CoLs is projected to decrease excepted over the Northern Cape where heavy and extreme precipitation days (RR > historical 75th percentile and RR > historical 95th percentile, respectively) attributed to CoLs may be more frequent. These changes are associated with a slight reduction of CoL annual frequency of and with a slight equatorward shift of their domain of occurrence in the studied region. Over the 21st century, these changes are expected to develop in parallel with decadal variability and with an increase in the inter-annual variability of CoL’s frequency.

Polar lows and Medicanes: Understanding how intense mesocyclones and their impacts might respond to climate change

S. Len (NCAS-Climate, Reading, United Kingdom)

Abstract details
Polar lows and Medicanes: Understanding how intense mesocyclones and their impacts might respond to climate change

S. Len (1)
(1) NCAS-Climate, Department of meteorology, Reading, United Kingdom

Abstract content

Polar Lows and Medicanes are very intense, small cyclones that occur in the Norwegian and the Mediterranean Seas. Although small in size, Polar Lows and Medicanes can generate damaging winds that have substantial impacts on shipping, coastal communities and infrastructure. Polar Lows and Medicanes have very symmetric structures, often having a central eye-wall that has led to them being referred to as Arctic Hurricanes and Mediterranean Hurricanes. Polar Lows and Medicanes are too small to represent in typical climate models. This means that there are very large uncertainties in how Polar Lows and Medicanes will respond to climate change, despite their large socioeconomic impacts.

This talk will discuss progress in simulating Polar Lows and Medicanes in global climate simulations performed at very high resolutions. The results of historical and climate change simulations with a 25km resolution version of the HadGEM3 climate model will be presented. The HadGEM3 simulations suggest that the frequency of both Polar Lows and Medicanes will decrease under climate change, primarily due to increases in the stability of the atmosphere over the Norwegian and Mediterranean Seas. However, there are some indications that when they do occur, Polar Lows and Medicanes may become more intense in a warmer climate. The potential for improving climate model projections of Polar Lows and Medicanes will also be discussed.

Forecasting heavy precipitation producing cyclones in the island of Crete

I. Tsanis (McMaster University, Hamilton, Ontario, Canada)

Abstract details
Forecasting heavy precipitation producing cyclones in the island of Crete

I. Tsanis (1)
(1) McMaster University, Civil Engineering, Hamilton, Ontario, Canada

Abstract content

The intensification of the hydrological cycle due to climate change will produce intense meteorological events, causing higher precipitation in shorter time periods. The island of Crete is located in the Eastern Mediterranean and is prone to high precipitation events which cause an increased risk of flash flooding.  The objective of this study is to obtain a better understanding of the hydrometeorological processes  that produce heavy precipitation in the island of Crete and result in flash flooding.  Effective forecasting for these natural disasters will increase public safety by reducing fatalities and changing the policy for a better flash flood risk management plan. For this purpose, images and datasets of the following parameters were used for the Eastern Mediterranean:  (a) Meteosat Meteorological Images (Infra-Red IR-10.8, 3h);  (b) Mean Sea Level Pressure ERA Interim (6h); (c) Wind at 500 hPa from ERA Interim (6h);  (d) Vorticity at 500 hpa from ERA Interim (6h); (e) Lightning (USLN Lightning Network - 3h) and (f) hourly  precipitation from Crete Meteorological Stations Network (3h).  At present, the data from the  15-17th of November 2012 storm event has been analyzed.  In this event, one of the  precipitation stations  located in the northwest part of the island of Crete, recorded more than 100mm of rain on 16/11/2012 and about 45mm of rain in the following day. More specifically, on 16/11/2016, 56.6mm of rain fell within one hour (14:00-15:00 UTC), and 27mm of rain on 17/11/2012 between 14:00-15:00 UTC. This severe rain event was caused by a cyclonic system approaching Crete from the Atlas Mountains, entering the Mediterranean on 15/11/2012, and moving to the east, with its center being located south of Crete.  The spatio-temporal distribution of the relative vorticity, wind speed, mean sea level pressure, lightning and the time of precipitation are used to shorten the forecasting time of a heavy precipitation event, in a probabilistic sense. More cases will be analyzed and presented in the conference, in order to validate the forecasting precipitation results in terms of sensitivity, specificity and accuracy.

Expansion of the tropics: evidence and implications

S. Turton (James Cook University, Cairns, Australia)

Abstract details
Expansion of the tropics: evidence and implications

S. Turton (1)
(1) James Cook University, College of Marine & Environmental Sciences, Cairns, Australia

Abstract content

There is accumulating evidence that the tropical zone is expanding poleward in both hemispheres. The implications of a poleward tropical expansion are significant; subtropical arid, conditions may be seen in regions at higher latitudes which have historically enjoyed a more temperate climate, with implications for management of water resources and agricultural systems. However, some regions which currently border the equatorial zone may experience an increase in extreme rainfall, which could result in flooding, the displacement of communities and increased incidence of disease. The poleward expansion of the Tropics appears to be linked to a concomitant expansion in the tracks of tropical cyclones, potentially bringing cyclonic activity to regions which have previously not experienced such weather events. Changes to the tracks and activity of cyclones, and other extreme weather events, will impact on human health, biodiversity and the economy. The burden of vector-borne diseases on health and the economy of the Tropics may also increase as more regions become climatically suitable for insect vectors. The Tropics are the most biodiverse region on earth, with more endemic species and more biodiversity ‘hotspots’ than anywhere else. However research suggests that although many species are tracking climate changes, species in the Tropics may be lagging behind the rate of tropical expansion – meaning some species may not be able to sufficiently track their preferred environment and climate and may potentially risk extinction. This paper explores the implications of expansion of the tropics for societies and environments in the tropics, who are likely to experience futures with no precedence.