Climate Modelling IV: GCMs Study Case

In parts I to III of previous climate modelling posts, we commented general aspects of climate models, how they work and also the main challenges and difficulties facing modellers.  In this fourth and final part of this series of posts, I want to show you an interesting application of Global Circulation Models (GCMs).

In Asia, the Mekong River (see Figure below), which is the 12th longest river in the world with a length of 4,350 kilometres, represents a fundamental source of resources for different economic activities in Southeast Asia, such as agriculture and fishing. Another fundamental aspect to consider is the strong intervention of the river with large hydraulic projects, such as dams for hydropower generation. Due to the river represents a fundamental source of resources for the different cities and human settlements located in the basin, interesting studies have been carried out in order to assess the potential effects of climate change in the Mekong River.

Mekong River 

Kingstonet al. (2011) explored the potential effects of global environmental change on water resources in the Mekong river basin and they also proposed a method to estimate the uncertainty of this prediction. For this purpose, they integrated GCMs with hydrological modelling. This method represents a really interesting approach to predict potential effect of climate change on the environment; different disciplines working together in order to create more sophisticated tools.

In addition, another significant contribution was to consider different climate scenarios given by a GCMs structure. Basically, they built different GCM scenarios working as a base for a hydrological model (SLURP) of the study area. The fundamental strength of this methodology was to observe modelled responses of the freshwater behaviour due to different climate scenarios. Specifically, they generated different global warming scenarios between 0.5 and 6.0°C. For the 2°C scenario, they used seven different GCMs. Although there were clear similarities among the GCMs, it was useful to use different models structures to analyse the influence of these structures in the final projection uncertainty.

Mekong River 

According to the main purpose of the study, the effort of researchers was mainly focused on the understanding and measurement of the model uncertainty. An interesting result was to find a significant effect on the uncertainty due to the differences in precipitation projections given by the different GCMs, even for the same scenario. As we could see in the previous post, one of the most relevant challenges facing GCMs modellers is to improve precipitation and water cycle simulation. This was also emphasized by other researchers in a study developed with multiple GCMSs in India, where were found severe uncertainties in future rainfall estimations. Conversely, a proper consistency was found in GCMs projection for both snowmelt season and evapotranspiration in the Mekong river basin.

Finally, the most significant outcome was related to the strong dependence of hydrological behaviour in the basin (discharge) with potential changes in precipitation patterns. Due to the seven GCMs applied and considering the different precipitation estimations of these, for the 2°C scenario the parameters of the hydrological model were numerically estimated with an uncertainty between -2.0 – 2.0% and the discharge pattern was suitably represented by the model (see Figures below).

As we can see, the obtained results ratify the proposed methodology of applying different GCMs in order to obtain a suitable estimation of the final uncertainty, minimizing this value and finally obtaining better projections. 

Mekong River, Parameter Uncertainty for HadCM3 (GCM) Model, 2°C Scenario

Mekong River, Monthly Discharge for Base – Line and Seven GCMs Applied, 2°C Scenario

COP 21: Never Reach ......... 1,5°C

Today is a historic day for humanity!.

That is the headline of many newspapers and web pages which have been following the international conference on climate change (COP21) in Paris. Today it was presented the final draft which summarizes two week of negotiations by representatives from 195 countries.

One of the most significant agreements is about the new target for global warming temperature. As we noticed in the previous post, the target of 2°C meant the starting point of the discussion for this version of the conference. Due to scientific evidence given along COP21 sessions, this goal changed: it's essential to pursue a lower value, with special efforts to restrict the increment to 1,5°C. According to categorical simulations this new target represents a significant and favourable change of scenery regarding to the potential effect on the global environment.

Another interesting point is related to finance. The funding of $100 billion per year by developed countries to support environmental policies in developing countries will start operating by 2020. This represents a substantial measurement to promote an integral solution with developing and developed countries working together. A global threat necessarily requires being tackled with a common view.

Although this represent an important advance facing the global warming, it´s necessary to be aware about what 1,5°C means; this figure must be analysed again, and again. Seems to be clear that the effect on climate change should be significantly less and probably some extreme consequences may be avoided by 2100, however, it´s still a 1,5°C increment; which are the environmental effects of this new scenery?. As can we see, environmental models and their continued progress have undoubtedly been (and they will remain being) a major player.

I invite you to take a look to the COP21 web page and read in detail this already called “historic document”. 

 “If it is adopted, this text will mark a historic turning point” (Laurent Fabius, president of COP21)

COP 21: Never Reach 2°C

As many of you may already know, these days from November 30 to December 11 it is holding the international conference on climate change COP21 (21st Conference of Parties) in Paris. Authorities from United Nations are carrying out negotiations in order to define effective measurements to keep the level of global warming bellow 2°C by 2100. But, why this number?, why 2°C?.

Although the debate around this figure is quite complex, the video below offers an interactive explanation for this value defined in 2009 by the International Panel on Climate Change (IPCC) in Copenhagen. The video summarize relevant environmental phenomena identified in the last two centuries such as relationship between sea level and pH, CO2 and global temperature, dynamic of Arctic sea ice, greenhouse anthropogenic emissions and trade-related CO2 transfers.

For the special purpose of this blog, considering the different perspectives that we have been discussing here, it is absolutely interesting to visualize the essential role of environmental models underpinning the analysis and projections of potential temperature and precipitation anomalies by 2100 (and their massive consequences) for each studied scenario.