Hello and welcome. Climate change is having many impacts in our planet. The increased emission of greenhouse gases together with land use change are leading to several changes in our climatic system. These changes are then leading to several other cascading consequences in different elements of our ecosystems and livelihoods. This figure here represent these main drivers of climate change in this internal circle, and on this intermediary circle, we see the most important consequences of these drivers in terms of changes in the climate. Then these changes in the climate have multiple impacts on our societies and ecosystems. But what are the actual evidence of climate change? What are the evidence that we have to show that different aspects of our climate are actually changing? One of the most important changes in the climate that had been very well-documented are the increased temperatures both in the land and in the ocean. In the last 100-120 years, more or less, global temperatures have increased on average about one degree Celsius, especially in the last 20-30 years. Although global temperatures don't increase equally everywhere, in general, the world is becoming hotter. This is a very unquestionable and undebatable evidence of climate change. Another evidence of climate change are the shrinking ice sheets, both in the Arctic and in the Antarctic areas. Due to warming oceans and warming surface temperature, these permanent ice sheets are melting. Especially in the last three to four decades, these have been very detectable and very significant impacts leading to significant reduction in the ice sheets in these areas. Also another important effect of climate change that is very visible is the retreat of glaciers in high mountainous areas. These permanent snow and ice that occurs in the top of mountains, they are also melting. Here are two of iconic examples of this; the Matterhorn peak in Switzerland in the 1960s and 2005 and Mount Kilimanjaro in Kenya and in 1993 and 2000 where we can clearly see the differences in the amount of snow and ice cover in these areas. The melting of these glaciers and permanent snow in high mountainous areas has been documented across mountainous ecosystems all over the world, and together with the melting of ice in polar zones, these has been leading to sea level rise. Speaking about sea level rise, also, we have robust evidence that shows that sea level has been rising steadily in the last century. It has risen between 20-25 centimeters in the last 100 years. About a third of that rise happened only in the last 25 years. Sea level rise occurs not only due to the melting of glaciers and of the ice in the polar areas, but also to the thermal expansion of ocean waters as they become warmer. Sea level rise can have very serious consequences to coastal ecosystems and coastal communities all over the world. They can directly impact urban and rural societies that occupy coastal areas across our planets. Another important change in the oceans that have been well-documented is the increase in the acidification of oceans. Our atmosphere now has much more carbon dioxide, CO_2, and part of this carbon dioxide gets absorbed by oceans, and therefore, the oceans become more acidic with a lower pH. This has consequences for several marine organisms, particularly organisms that use carbonate as a building block such as many species of shellfish, and corals, and etc. Ocean acidification has also an important effect in several marine organisms and consequently to human societies that explore these resources. We have also plenty of evidence that support that extreme events such as extreme floods, extreme drought, extreme heat waves are becoming more and more frequent with time. These events have always happened in the past, but now, they're simply becoming more intense and are happening more often. In Europe, for example, which is this example that I brought here, there is a robust evidence showing that extreme events have been increasing since the '80s, at least, especially the number of extreme flood events represented here in this graph with this blue line. Also, extreme events such as the unusual drought that happened in Europe between 2018 and 2019 are also expected to occur more often in the future. Extreme events have been occurring more often in the past, and they are also expected to occur more often in the future. This might have several consequences for ecosystems as well. Changes in rainfall, they are more heterogeneous and harder to generalize. We can see here the documented changes in rainfall in the first half of the 20th century here and on the second half of the 20th century. We can see that some areas have actually become wetter, especially large areas here in the Northern Hemisphere, while other areas have become drier with time in regions, for example, such as West Africa or Eastern China. In any case, there have been pronounced changes in rainfall in the last century, and these changes are also expected to persist and intensify in the future. The example of rainfall, it's also very illustrative in the sense to show that climate change impacts can be very heterogeneous in space. In the case of rainfall, they can even go in opposite directions. But these, especially heterogeneous impacts of climate change, they're actually observed in all measurements that we have for climate change. For temperatures, for example, represented in these two lower graphs here, although there is a general tendency of increasing temperatures globally, not all areas will warm up in the same way. So projected temperatures increases in the future, for example, are much higher in some regions such as polar zones, for example. So climate change, although it's a global phenomenon, it's very spatially heterogeneous phenomena. It does not affect all regions and ecosystems in the same way. Just as climate change impacts themselves are spatially heterogeneous, so is our knowledge about climate change. These maps here, they show the distribution of weather stations that collect information on precipitation and temperature, which is the basis of information based on which we build our climatic models and we build our understanding of climate change. As we can see, some regions have many more climate station than others. Our knowledge on climate change is also very spatially biased. We know much better what's going to happen and what has been happening in some regions than in other regions. This has certainly implications in terms of restricting our thorough understanding of climate change across the globe. A few take-home messages. Climate change is clearly visible and detectable in different elements of our planet. Among these, the most important ones are the global temperature rise, the shrinking ice sheets and Arctic sea ice, the glacier retreat in mountainous ecosystems, the sea level rise, the impacts on ocean acidification, and the increased occurrence of extreme events. However, these impacts of climate change are not equally distributed across the planet. Climate change is spatially very heterogeneous. Our knowledge and information on climate change is also very spatially biased. We don't know with the same level of accuracy what are the consequences of climate change in all areas across the world. Thank you very much for your attention.
