15 April 2021 | Duration of reading: 9 min

By João Paulo Brêda

Climate change has been a prominent theme in recent decades. This issue has been linked to the process of indiscriminate industrial development and ended up raising many environmental movements around the world. Political and inflammatory demonstrations brought debates that often disassociate themselves from science. Even though there is important research on the subject, there are still doubts and misinterpretations that lead to shallow, incoherent and biased discussions.

          To begin, it is important to understand that climate variability is a natural process. On a scale of decades, we are faced with climatic phenomena such as El Niño and La Niña, which are related to temperature anomalies in the Pacific Ocean and significantly change the rain regime not only in the Amazon region but in several places in Brazil and the world ((more information about El Ninõ and La Ninã). On a scale of centuries and millennia, there are major climatic changes such as the appearance of ice ages (the latter 20,000 years ago) and other less abrupt periods such as the “Little Ice Age” between 1500 and 1800 d.c. For more information on paleoclimatology, see the texto by researcher Rafael Reis, which discusses the past climate in the Amazon region, published read more at Conexões Amazônicas.

          However, the mobilization of scientists and world leaders consolidated through the IPCC IPCC (Intergovernamental Panel on Climate Change) highlights the human influence on the world climate. This is an attempt to reduce the effects on something that, unlike the natural climate variability, we have a certain responsibility. In urban areas, effects on climate due to anthropic actions are easily noticed, as is the case of thermal inversion and temperature increase due to the reduction of green areas (heat islands). On a global scale, the human effect on the climate comes down to consequences from greenhouse gases (GHG) emissions to the atmosphere. However, this effect is not so noticeable because it consists of a complex process that is mixed with natural variations that occurs between years, seasons, and due to specific atmospheric phenomena.

          An alternative to detect and project these impacts is to use current scientific knowledge in the development of climate models. Climate models are mathematical tools that represent, in the form of physical equations, the balance of mass and energy that occurs in the atmosphere, oceans, soil and glaciers. They are able to simulate approximately the current climate of the planet and make predictions using projected concentration of GHGs in the atmosphere as input data. These models then provide climate information such as: temperature, rain, air humidity, atmospheric pressure, among others.

          To obtain more accurate estimates of the impact on water resources, we forced a hydrological model with output data from climate models. With a similar concept, hydrological models use rainfall data as an input to simulate runoff, infiltration, evapotranspiration and soil moisture variation in river basins, and usually also estimate river flows. In the Figure 1 below we highlight the Amazon Basin, which is one of the study areas from our research about projections of climate change impacts on water resources related to the end of that century (2080-2100), a work carried out within the Large Scale Hydrology research group, at the UFRGS Hydraulic Research Institute (Link).