**2. Simple methods to quantify the climate change**

## **2.1 Data**

260 Studies on Water Management Issues

In the last two decades, global climate change has continuously been gaining importance. Scientists from different disciplines agree that our climate is continuously changing. The question open to discussion and debate is the importance and the relative influence of

The first study related to climate change was initiated in California University by a climatologist named Charles Keeling. In 1958, he started to monitor the amount of atmospheric carbon dioxide in Mauna Loa observatory located on Hawaii. His studies, which were continued by his son Ralph Keeling after his death, indicated that atmospheric carbon dioxide is continuously increasing. Figure 1, also known as the Keeling Curve

The atmospheric carbon dioxide investigation of Charles Keeling is considered to be the first

In 1970's and 1980's climate change was usually considered as global warming by scientist from various disciplines and interpreted according their knowledge. In late 1980's however it was clear that a more integrated approach is needed to investigate the climate change. Global climate change was considered a complex topic with many aspects and policy and

To cover these needs, World Meteorological Organization (WMO) and United Nations Environmental Programme (UNEP) founded together the International Panel of Climate

Since early 1990's, IPCC published comprehensive reports in regular intervals the last one being published in 2007 (IPCC, 2007). Simulation results from IPCC modelling studies

decision makers needed objective information on climate change including

**1.1 A general summary of climate change** 

human activities on the climate.

illustrates the trend of this increase.

Fig. 1. Keeling curve

• Its reason

• Possible solutions

Change (IPCC) in the year 1988.

milestone in climate change studies.

• Environmental and socioeconomic effects

Data related to climate change are on two different temporal scales. The first of these data is the so-called paleoclimatological data that is indirect. Stable isotope data dating back hundreds thousands of years back is used to reconstruct the past atmospheric composition and basic atmospheric conditions such as temperature, precipitation. The second type of data is the historical data from observations dating approximately two centuries back at most. Long term time series of meteorological data can be used to analyse the recent climate dynamics.

Managing the Effects of the Climate Change on Water Resources and Watershed Ecology 263

Regional climate models (RCM) have a higher spatial and temporal resolution. They provide more detailed information then the GCMs, however they work on a smaller domain. RCMs work by increasing the resolution of the GCM in a small, limited area of interest. An RCM usually cover an area the size of Western Europe or southern Africa. GCMs determine very large scale effects of changing greenhouse gas concentrations, volcanic eruptions etc. on global climate. The climate (temperature, wind etc.) calculated by the GCM is used as input at the open boundaries of the RCM. RCMs can resolve the local impacts given small scale information about orography, land use etc., giving weather and climate information at fine horizontal resolutions such as 50 or 25km. The outputs of RCMs are used to force finer spatial resolution models that are used to predict the response of watershed ecosystems to climate change that are briefly explained in the next section.

**2.3 Models related to prediction of response of watershed ecosystems to climate** 

Many environmental models that are useful to predict the response of watershed ecosystems to climate change are available. Most of these models are freely available, even open source. Giving detailed information about environmental modelling is beyond the scope of this text. For such information, the reader is referred to other standard texts such as

Basically, there are two general types of models that are used to predict the response of watershed ecosystems to external forcing such as climate change: The watershed models

Watershed models are derived from hydrological models, usually from a formerly known hydrological model so that they contain all the key hydrological processes. They also

Since 1960's many hydrological models were developed and some of them evolved to general purposed watershed models. However, just a minor fraction of them were designed to simulate the hydrology and ecology of entire watershed using the coupled modelling approach and even fewer of them were continuously developed and became widely used, freely available open-source modelling tools. SWAT (Arnold et. al., 1999) and HSPF (Brickner et. al, 2001) are good examples for such modelling tools. WASH123D (Yeh et. al, 2005) is more comprehensive than SWAT and HSPF as a hydrological model but has simpler water ecology related facilities. MIKE-SHE is also capable to simulate the watershed hydrology and ecology; however it is neither free nor open source; and needs additional products such as MIKE-11 to be coupled with. Other models such as SWAP (Van Dam, 2000; Van Dam et al., 2008), PIHM, Hydrogeosphere (Therrien et al, 2010) are general hydrological model taking almost all the compartment of the hydrological and can be easily linked to

Among all the models discussed SWAT and HSPF are the most widely used ones and generally most applicable ones. The applicability of SWAT was reviewed by Gassmann et al

contain sediment transport and terrestrial biogeochemical cycle related processes.

**2.2.2 Regional climate models** 

Schnoor (1996), Chapra (2008) or Simonovic (2009).

and the aquatic ecosystem models.

landscape and water ecology models.

**2.3.1 Watershed models** 

**change** 

Meteorological data can be obtained from state agencies; some of the free data is available on the internet as well. WMO is responsible to organize and manage the meteorological data globally. Meteorological data on territories without meteorological stations can be interpolated using many techniques included models. Results obtained using these techniques are post processed, reanalyzed and published; usually on regional scale such as Europe for example. There are several European community projects that provide such data.

Globally, meteorological data from 1960 to 2000 was used to calibrate and validate global climate change models that will be briefly described in the next section.
