Top PDF Simulations and Mechanisms of Subtropical Low-cloud Response to Climate Change

Simulations and Mechanisms of Subtropical Low-cloud Response to Climate Change

Simulations and Mechanisms of Subtropical Low-cloud Response to Climate Change

heat of vaporization approaching zero in which all SGS closures should represent dry turbulence. The lack of consistency between turbulence and convection schemes have been shown to produce unphysical low cloud behaviors, induce current day biases on low cloud cover, and contribute to the disagreement in the predicted climate response (Nuijens et al., 2015; Brient et al., 2015). Therefore, a unified and physically consis- tent parameterization scheme is important for realistically representing low clouds in GCMs and reducing the model uncertainty of low cloud responses to climate change. LES can explicitly simulate the dynamics of boundary layers and clouds, and they have been successful in reproducing the observed boundary layer structures, if realistic current-day forcing is given. However, to understand the climate-change response of low clouds, LES must be coupled to large-scale forcing representing future climate for which no observation is available. Therefore, simple assumptions are usually made for these scenarios, such as fixing the SST increase to match that of the free troposphere, effectively fixing the SST gradient between the subtropics and the tropics. The surface energy budget is not closed, and the surface latent heat flux (LHF) may increase according to the Clausius-Clapeyron relation (Rieck et al., 2012), far exceeding the decrease in the sea-surface net longwave (LW) cooling. Under such assumptions, the ocean acts like an infinite heat bath that can feed this LHF increase. It is unlikely that the ocean circulation can respond so efficiently to maintain the SST gradient. The large-scale forcing of the atmosphere also suffers similar problems, for which the change of upper-tropospheric temperature and the CO 2 forcing might not be coherent.
Show more

199 Read more

Investigating the sensitivity of numerical model simulations of the modern state of the Greenland ice-sheet and its future response to climate change

Investigating the sensitivity of numerical model simulations of the modern state of the Greenland ice-sheet and its future response to climate change

Firstly, several other potential temperature datasets over Greenland exist to force the Glimmer ice-sheet model. A new parameterisation based on more up-to-date automatic weather station data, for instance, is now available with a similar form to Eqs. (6) and (7) (Fausto et al., 2009). How- ever, for this work we chose the ERA-40 derived temperature product for consistency with the new precipitation dataset. Furthermore, datasets also exist in terms of satellite products. For satellite datasets, temperature data are available from the Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder (APP) from 1982–2004 which is collated twice a day at the local solar times of 14:00 and 04:00. Al- though the data is initially on a 5 km resolution it is sub- sampled at 25 km pixels. The APP-x product includes all- sky surface temperature with the cloudy-sky surface tem- peratures calculated using an empirical relationship between clear-sky surface temperature, wind speed, and solar zenith angle (daytime). However, this only applies to surface tem- peratures over sea-ice and not land. Therefore, temperatures over Greenland are based only on data from clear-sky re- trieval with temperatures in cloudy regions interpolated from clear-sky areas. Although useful for comparing with present day surface temperatures from climate models, this dataset is not suitable to directly force an ice-sheet model over Green- land because (a) the largest uncertainties are likely to be over Greenland (J. R. Key, personal communication, 2010), (b) no associated orography exists which is used to downscale from the resolution of the forcing data onto the high-resolution of the ice-sheet model and (c) sensitivity studies using Glim- mer indicate that the APP-x temperatures were significantly too low, in observed ice-free regions such as western Green- land, (by up to 12 ◦ C in western Greenland compared with EISMINT-3 temperatures which have at least been derived from surface observation) to reproduce a reasonable mod- ern day ice-sheet without tuning ice-sheet model parameters beyond uncertainty ranges. This could, in part, be due to the satellite recording ice surface temperatures rather than air temperature. Furthermore, clear-sky retrievals errors are predominantly due to uncertainties in cloud detection (Key et al., 1997) particularly during the night. The low temper- atures, bright surface and high elevation make remote sens- ing over Greenland particularly difficult in terms of accurate cloud detection.
Show more

21 Read more

Mechanisms of Heat Content and Thermocline Change in the Subtropical and Subpolar North Atlantic

Mechanisms of Heat Content and Thermocline Change in the Subtropical and Subpolar North Atlantic

The different mechanisms dominating the heat convergence response for each gyre are probably a fundamental consequence of how heat is transported over the basin. For a climate mean, the northward heat transport is carried by MOC contributions, mainly over the upper 100 m at low latitudes and from 100 to 1300 m at middle-to-high latitudes, and augmented by a gyre con- tribution at high latitudes (Fig. 6). The winds dominate these low-latitude changes in heat transport by the MOC over the upper 100 m through the Ekman response; for the same wind stress perturbation, the Ekman response is larger in magnitude at low latitudes as a result of the smallness of the Coriolis parameter. The northward heat transport can equivalently be viewed as being carried by a series of contributions: an Ekman cell at low latitudes, a MOC-minus-Ekman cell at middle and high latitudes, and a gyre contribution at high latitudes (Williams et al. 2014). Thus, the sensitivity of the ocean heat content to atmospheric forcing varies within the basin according to how the heat transport and convergence is achieved.
Show more

13 Read more

The Impact of Climate Change on Hydroecological Response in Chalk Streams

The Impact of Climate Change on Hydroecological Response in Chalk Streams

Summary statistics of LIFE projections, proxy for hydroecological response or river health. Excess kurtosis is a measure of the[r]

18 Read more

Storm Track Sensitivity to Resolution and Climate Change in High-Resolution Global Simulations.

Storm Track Sensitivity to Resolution and Climate Change in High-Resolution Global Simulations.

Current GCMs typically have a horizontal gridscale of more than 100km, which is much too coarse to resolve mesoscale processes. Since we know latent heating and diabatic effects strengthen cyclones through a positive feedback, in which the heat released strengthens the storm, it is reasonable to question whether these global studies would find different responses to climate warming if they were able to resolve fine scale latent heating explicitly. Although climate models can generally resolve the structure of extratropical cyclones, studies have shown that frontal gradients are sharper at higher resolution (Catto et al. 2010). Studies have also shown that the intensity of cyclones is better represented as resolution increases from 100km to 20km grid-spacing (Jung et al. 2006; Champion et al. 2011; Willison et al. 2013; Zhang et al. 2018). Overall, cyclones are present at coarse resolutions, but what about their frequency, intensity, and associated rainfall?
Show more

127 Read more

Impacts of climate change on low flows in the Rhine basin

Impacts of climate change on low flows in the Rhine basin

Middelkoop et al. (2001) have used a set of models, to assess the effects of climate change on the discharge regime in different parts of the Rhine basin using the results of UKHI and XCCC GCM- experiments. All models indicated similar trends regarding the observed values: higher winter discharge as a result of intensified snow melt and increased winter precipitation, and low summer discharge due to the reduced winter snow storage and an increase of evapotranspiration. Both climate models indicate a shift of the hydrological regime in the entire Rhine basin. In the upper Alpine area the intra-annual difference between a low winter flow and a high summer flow decreases (and even may be inverted), while in the lower parts the existing summer-winter differences are amplified. The average annual number of days with a Rhine discharge at Lobith is below 1000 m 3 /s may increase from 19 (under present day conditions) to 26 according to the XCC2050 scenario and 34 according to the UKHI2050 scenario for the year 2050; both scenarios have used the IPCC emission scenario IS92a with a global climate sensitivity of 2.5 ⁰C. (Middelkoop et al.,2001)
Show more

63 Read more

Climate change, the Great Barrier Reef and the response of Australians

Climate change, the Great Barrier Reef and the response of Australians

ABSTRACT Inspiration, aspirations, attitudes, and perception of threats play a pivotal role in the way that individuals associate themselves with natural environments. These senti- ments affect how people connect to natural places, including their behaviours, perceived responsibility, and the management interventions they support. World Heritage Areas hold an important place in the lives of people who visit, aspire to visit, or derive a sense of security and well-being from their existence. Yet, the connection between people and special places is rarely quanti fi ed and policymakers fi nd it dif fi cult to incorporate these human dimensions into decision-making processes. Here we describe the personal concern and connection that Australians have with the Great Barrier Reef and discuss how the results may help with its management. We utilize a statistically representative sample of Australian residents ( n = 2,002) and show empirically that climate change is perceived to be the biggest threat to the Great Barrier Reef, and that the Great Barrier Reef inspires Australians, promotes pride, and instills a sense of individual identity and collective responsibility to protect it. An increased understanding of the high levels of personal connection to iconic natural resources may help managers to enhance public support for protecting climate-sensitive systems within Australia and around the world.
Show more

8 Read more

Crop failure rates in a geoengineered climate: impact of climate change and marine cloud brightening

Crop failure rates in a geoengineered climate: impact of climate change and marine cloud brightening

Climate change as a result of anthropogenic in fl u- ences, such as burning fossil fuels and altering land use, is having an impact across the world (Stocker et al 2013). There have been several methods suggested to ameliorate some of the effects of climate change, via either mitigation or explicit geoengineered modi fi ca- tions. One such geoengineering method is marine cloud brightening, which was originally suggested nearly 25 years ago (Latham 1990). Marine cloud brightening, which is a solar radiation management (SRM) method of geoengineering, has the aim of preventing adverse temperature changes (Shepherd 2009, Jones et al 2009, 2011, Latham et al 2012a) and has been suggested as a method of restoring polar sea ice coverage (Latham et al 2012a, Parkes et al 2012) and reducing coral bleaching (Latham et al 2013). It involves seeding unpolluted marine stratocumulus clouds in an effort to increase the cloud droplet number and thus reflectivity (Twomey 1977). Marine cloud brightening alters the water cycle of the planet
Show more

7 Read more

The Monash Simple Climate Model experiments (MSCM-DB v1.0): an interactive database of mean climate, climate change, and scenario simulations

The Monash Simple Climate Model experiments (MSCM-DB v1.0): an interactive database of mean climate, climate change, and scenario simulations

tivity experiments in which elements of the climate system are turned off in various combinations are used to address (1) and (2). This database currently provides more than 1300 experiments and has an online web interface for fast anal- ysis and free access to the data. We briefly outline the de- sign of all experiments, give a discussion of some results, put the findings into the context of previously published re- sults from similar experiments, discuss the quality and limi- tations of the MSCM experiments, and also give an outlook on possible further developments. The GREB model simula- tion is quite realistic, but the model without flux corrections has a root mean square error in the mean state of the sur- face temperature of about 10 ◦ C, which is larger than those of general circulation models (2 ◦ C). It needs to be noted here that the GREB model does not simulate circulation changes or changes in cloud cover (feedbacks). However, the MSCM experiments show good agreement to previously published studies. Although GREB is a very simple model, it delivers good first-order estimates, is very fast, highly accessible, and can be used to quickly try many different sensitivity exper-
Show more

25 Read more

Consultation Submission on the Climate Change Response Bill 2010

Consultation Submission on the Climate Change Response Bill 2010

A fully-effective Climate Change Bill when enacted will for the first time provide a domestic legislative base in Ireland for fully incorporating climate change considerations right across the policy making process. It should also provide enhanced certainty for all stakeholders, particularly the business community and government departments, on Ireland’s overall mitigation ambitions. This would greatly assist the creation of a truly national framework for designed transition towards a low to zero carbon and fully resource efficient society. As a result, the importance and significance of this legislation should not be underestimated, particularly in relation to the potential contribution it will make towards sustainable development.
Show more

8 Read more

Tributaries affect the thermal response of lakes to climate change

Tributaries affect the thermal response of lakes to climate change

Van Vliet et al. (2013) suggested that river discharge and air temperature should be used while predicting future river temperatures. We incorporated recent findings of climate- induced changes in air temperature and river discharge regimes to model both future river temperature and SSC. Sea- sonal mean predictions for air temperature increase in west- ern Switzerland (Fig. 2) were estimated from CH2011 (2011) for the A1B emission scenario (balanced use of renew- able and fossil fuels) using results from 20 regional cli- mate models. Flow projections were obtained from published results generated by the PREVAH (PREcipitation-Runoff- EVApotranspiration HRU Model) hydrological model (Vivi- roli et al., 2009) using a gridded configuration as described in Speich et al. (2015) and Kobierska et al. (2011). The model explicitly incorporates changes in glacial extent, snow melt, catchment runoff, floods and low water flows (FOEN, 2012; Bosshard et al., 2013; Speich et al., 2015). The PREVAH outcomes for the 1981–2009 period have been validated with data from 65 river gauges (Speich et al., 2015), including the two gauges upstream of LG (Rhône; no. 2009 in Fig. 2) and LB (Aare; no. 2085 in Fig. 2) used here.
Show more

21 Read more

Observed groundwater temperature response to recent climate change

Observed groundwater temperature response to recent climate change

Abstract. Climate change is known to have a consider- able influence on many components of the hydrological cy- cle. Yet, the implications for groundwater temperature, as an important driver for groundwater quality, thermal use and storage, are not yet comprehensively understood. Fur- thermore, few studies have examined the implications of climate-change-induced groundwater temperature rise for groundwater-dependent ecosystems. Here, we examine the coupling of atmospheric and groundwater warming by em- ploying stochastic and deterministic models. Firstly, several decades of temperature time series are statistically analyzed with regard to climate regime shifts (CRSs) in the long-term mean. The observed increases in shallow groundwater tem- peratures can be associated with preceding positive shifts in regional surface air temperatures, which are in turn linked to global air temperature changes. The temperature data are also analyzed with an analytical solution to the conduction– advection heat transfer equation to investigate how subsur- face heat transfer processes control the propagation of the surface temperature signals into the subsurface. In three of the four monitoring wells, the predicted groundwater tem- perature increases driven by the regime shifts at the sur- face boundary condition generally concur with the observed groundwater temperature trends. Due to complex interac- tions at the ground surface and the heat capacity of the un- saturated zone, the thermal signals from distinct changes in air temperature are damped and delayed in the subsurface, causing a more gradual increase in groundwater tempera- tures. These signals can have a significant impact on large- scale groundwater temperatures in shallow and economically important aquifers. These findings demonstrate that shallow
Show more

14 Read more

Getting it : expert perspectives on the corporate response to climate change

Getting it : expert perspectives on the corporate response to climate change

One business opportunity, in principle, relates to cost savings from better energy efficiency or resource productivity. There are long-standing issues about why there hasn’t been better take up. These are to do with the relative prices of resources and labour, the relative connectedness of energy costs with capital costs, and the rates of return. Energy-efficiency investments are still competing for capital with other investments with higher rates of return. Because there isn’t full cost accounting across the business or industry, the benefits of the energy-efficiency investments are not seen. There are similar issues with renewables technology. There needs to be support for these sectors at the stage where they don’t have critical momentum. If the money is not visible, people won’t rush to that sector. This is about creating the conditions in which there is a viable model. Sometimes that will mean public sector subsidy, particularly in the early stages because of the inertia around changing business models and the need for capital investment to be ring-fenced and protected, as learning and costs come down. This is about creating The business world’s response to the climate change
Show more

24 Read more

Factors Affecting Agriculture in Response to Climate Change in Bangladesh

Factors Affecting Agriculture in Response to Climate Change in Bangladesh

B.Sc.Ag.(Hons) from the Department of Agriculture, Noakhali Science and Technology University, Bangladesh.. 26.[r]

16 Read more

Hybrid Legal Approaches Towards Climate Change: Concepts, Mechanisms and Implementation

Hybrid Legal Approaches Towards Climate Change: Concepts, Mechanisms and Implementation

quite modest on legal findings and it negatively impacts the knowledge transfer to the legislators. Law needs (good) science, which should be used in a legal conclusive manner when shaping international law. At policy level, the litigation and legal angle could improve significantly after 2015, yet only if the legal design of the agenda within the United Nations Framework Convention on Climate Change would address im- mediate legal requests for expanding adaptation duties, define the gap between adaptation and damage(s), and explore options in other fora (e.g., migration/refugees). In the medium term, the outcome of COP 21, the Paris Agreement, selects tools or particular types of damage and en- sures that a “baseline approach“ is considered, parameters (triggers) are assessed in order to avoid individual baselines, and that there is no cir- cumventing mitigation and/or adaptation. With the Paris mandate, policy makers should start addressing the long-term and sensitive issues of com- pensation/finance at the various levels (nation state, community, individual). 42
Show more

14 Read more

Crop yield response to climate change varies with cropping intensity

Crop yield response to climate change varies with cropping intensity

Analysis of observed global data and regional crop modelling demonstrate that 19 areas of high versus low cropping intensity can have systematically different yields, in both 20 observat[r]

23 Read more

Heinrich events show two-stage climate response in transient glacial simulations

Heinrich events show two-stage climate response in transient glacial simulations

and 25.7 ka (A2). From ExB and ExC, we obtain two Hein- rich events starting at 22.4 ka: B1 and C1. Later Heinrich events show an interference of the deglaciation and are dis- carded. All experiments were forced with transient insola- tion and greenhouse gas concentrations from reconstructions (Berger, 1978; Spahni and Stocker, 2006a, b; Lüthi et al., 2008). The Antarctic Ice Sheet and the bedrock topography outside the ice sheet domain were prescribed based on the ICE-5G 21 ka topography (Peltier, 2004). The topography is corrected for a global uniform sea level change computed from the modeled ice volume. In ExA and ExB, the dy- namic river discharge scheme routes the Nile into the Red Sea during the glacial. In ExC this scheme is improved and the Nile always feeds into the Mediterranean. The technical differences among the three experiments are small enough to consider them comparable. We chose these simulations as a technically quasi-identical subset from various simulations that were performed when working on a model that is able to simulate the last deglaciation. As the simulations consumed considerable resources, we refrained from performing a ded- icated ensemble, but made use of the available data.
Show more

16 Read more

Local impact analysis of climate change on precipitation extremes: are high resolution climate models needed for realistic simulations?

Local impact analysis of climate change on precipitation extremes: are high resolution climate models needed for realistic simulations?

A comparative study between the convection-permitting cli- mate models with a spatial resolution from 2.8 up to 40 km and driving GCMs or reanalysis data was performed to check whether the models with higher resolution provide more ac- curate precipitation simulations. Another analysis was per- formed to validate the spatial-scale independency assump- tion of climate change signals for the delta change down- scaling method. The results show that, whereas winter daily precipitation extremes are generally overestimated by the ALARO and CCLM models, improved results for summer precipitation extremes are observed, especially for sub-daily timescales. This suggests the added value of convection- permitting climate models to simulate summer sub-daily ex- tremes because of either better representation of deep con- vection or more detail of the land surface. The results more- over indicate that the difference between the convection- permitting models and the parent GCMs or reanalysis data decreases as the timescales get larger (i.e., weekly and monthly). Based on the precipitation statistics derived from IDF curves, the ALARO and CCLM models mostly under- estimate local sub-daily precipitation, but still better simu- late it compared with parent GCM or reanalysis data when available. Higher precipitation intensities by finer-resolution models are a result of better representation of small-scale convective precipitation by these models.
Show more

15 Read more

Declining uncertainty in transient climate response as CO2 forcing dominates future climate change

Declining uncertainty in transient climate response as CO2 forcing dominates future climate change

Based on data from Intergovernmental 17 Panel of Climate Change IPCC reports, we show that the evolution of increased 18 anthropogenic forcing and its reduced relative uncertainty betwee[r]

20 Read more

Approaches to implementing a strengthened global response to the threat of climate change

Approaches to implementing a strengthened global response to the threat of climate change

to consider both overshoot and non-overshoot pathways as available in the literature. The importance of assessing the mitigation pathways on both global and regional scales was pointed out. The description of these pathways will need to cover energy use, land use, agriculture and food systems, different technologies and the various emissions by sector, and will assess the technological and socio-economic implications. The need for consideration of timescales of action, emissions levels and climate responses, timing of net zero emissions, including the interdependence between short- and long-term action and between extent of overshoot and end of century emissions levels, was emphasized. There is also a specific request from the UNFCCC to provide a 2030 emissions level for 1.5°C. The assessment should focus on sectors and across sectors and consider both demand- and supply-side. The discussion pointed to the importance of distinguishing the two concepts of “being consistent with 1.5°C” and “being required for 1.5°C” in the assessment of pathway characteristics.
Show more

47 Read more

Show all 10000 documents...