COP28 et adaptation au changement climatique : l’enjeu des données
Adapting to climate change is at the heart of the COP28 negotiations. Agriculture, which must cope with droughts, heat waves, and floods, is particularly affected by these adaptation needs. To achieve this, climate modeling based on global and local data is essential to better understand the future climate and lead sustainable transitions. The FARM Foundation invites Benjamin Sultan, a researcher at the IRD, LResearch Institute for Development to discuss climate change, adaptation opportunities and data issues.
FARM Foundation: Why is adaptation essential for agriculture today?
Benjamin Sultan: Climate change poses a real threat to agriculture. Temperatures are rising, exacerbating the risks of heat stress on plants and animals. There is also an increase in the frequency of extreme events such as droughts and floods. In the Global South, these risks affect already fragile production systems that must feed a rapidly growing population. Of course, these risks also affect countries in the Global North, such as France during the summer of 2022, which experienced a nearly 3°C increase compared to the 1900-1930 normal, with agricultural yields falling by 10 to 30%.
Agricultural systems are now out of balance due to the abrupt change in climate and are struggling to adapt. Yet we have persisted, trying to irrigate more, apply more fertilizers and pesticides. The prime example is corn in the Mediterranean, a water-intensive crop that is not resistant to heat and is no longer suited to the Mediterranean climate.
FARM Foundation: Could you explain to us what climate analogues are?
Benjamin Sultan: Climate analogues allow us to understand and visualize what the climate of a given area will be like in the future based on examples that already exist in the current world. This work is done using climate simulations and has already been applied to large cities.
For example, by 2050, we observe that the future climate of the city of Lisbon will be very close to the current climate of the city of Algiers. Paris will be quite close to Madrid.
We have a kind of gap where each city can imagine its own climate by going down a few degrees in latitude, or by going up a few degrees in the southern hemisphere. In the Mediterranean, we know that the northern shore – in other words, southern Europe – is expected to become significantly drier and warmer. We will then find a climate that will resemble what we know today in Morocco, Tunisia, or Algeria.
On the other hand, there are places in the world where there is no climate analogue. For example, some regions of the Middle East will exceed 50°C with the effect of climate change. These are climates we have never experienced anywhere else in the world. We will also have very specific conditions in tropical regions – in the Sahel, even in the Amazon – due to a combination of high humidity and high temperatures causing significant thermal stress and heat waves that could be more deadly in these regions than in those where temperatures are simply higher but without high humidity.
Climate analogues: extent of change in climatic conditions in major cities in 2050
Source : Bastin et al., 2019, “Understanding climate change from a global analysis of city analogues”
As this map shows, cities represented by green dots are those for which future climate conditions correspond to climates experienced today in other major cities—that is, cities with identifiable climate analogues. Conversely, cities colored red are those for which future climate conditions do not correspond to any climate experienced today in the world. They are particularly concentrated in tropical areas. The size of the dots represents the extent of change between current and future climate conditions.
FARM Foundation: From an adaptation perspective, what is the interest of climate analogues for the agricultural sector?
Benjamin Sultan: They are useful for finding adaptation solutions by identifying varieties or cultivation methods in a region that is already experiencing the constraints that we will experience later, and where farmers have started to select varieties and adopt practices better suited to these climatic conditions. To take the example of corn in the Mediterranean, which will experience a significant drying out, sorghum could be adopted, drawing inspiration from the African example.In fact, it has been selected for years in the Sahel because of its resistance to droughts and high temperatures.
However, these imported agricultural practices must also adapt to cultural factors – be accepted by farmers and integrate into the landscape – and to socio-economic factors, responding to demand and a market.
FARM Foundation : In one of your recent publications, you mentioned the need to strengthen observation networks, particularly on the African continent. Could you explain the issues behind this lack of data?
Benjamin Sultan : There are indeed significant disparities in terms of information, particularly in Africa. The observation network there is less dense and of lower quality, limiting our ability to study the evolution of climate change and its consequences. Recent conflicts also hamper access to data, with fewer and fewer observations to characterize the effect of global warming. Nevertheless, we can continue to collect data—under certain conditions—through IRD partners, particularly in Niger and Burkina Faso. Despite this, there are regions like Mali where the IRD has had observation networks on vegetation, agriculture, or pastureland for decades, which are now inaccessible due to insecurity.
Sharing observations is also essentialIn Africa—at least in the regions I know—there is a transparency problem because the data is not public. It is rarely shared, and even if it does exist, it will not be used by research for weather forecasting. It can also be of poor quality because it is not subject to peer review. Therefore, reflections on adaptation itself can be based on old or poor-quality data.
For climate modeling and analogues, we use global data that integrates satellite images covering the entire globe. To evaluate and validate these data, they can be combined with data from local stations. This means that in our studies or even in IPCC reports, we often use datasets that contain more uncertainty for countries in the South, while they are very reliable for countries in the North.[1].
At the level of the World Meteorological Organization (WMO), there are also gaps in the information system at the level of African countries.[2]Nearly a quarter of observations never reach the WMO. This is due to a multitude of factors: the network is down, the data is not transmitted, there is a conflict at a certain location, etc.
Since COP21, programs on data rescue, on the use of data itself, and on early warning systems have nevertheless emerged. The program CREWS (Climate Risk and Early Warning Systems) was, for example, partly supported by France at the time of COP21. However, data disparities persist between countries in the North and South.
FARM Foundation : What can we expect from COP28?
Benjamin Sultan : This is a truly important COP because it will allow us to conduct the first global assessment of the Paris Agreement. We already know that we are not on the right trajectory and that we will have to correct it. At the same time, for the countries of the South, there are many challenges. We, the countries of the North, are asking them to change their model, not to take the same trajectory as us on energy, even though they do not have the financial means to do so at the moment. A particular expectation will be on the global assessment of adaptation in order to better direct efforts.This assessment will have to answer two questions: How is adaptation measured? And in which countries is adaptation taking place or not taking place due to a lack of investment?
The adaptation challenges are therefore multiple. First, in terms of data, it is essential to be able to access quality information over the long term in order to identify reliable trends in extreme events linked to climate change and to better understand the future climate of certain highly vulnerable regions.
With a shift in biogeographies in latitude, the transfer of knowledge is also essential both from North to South and from South to North, particularly with regard to agricultural practices, more adapted varieties, etc.
[1] The difficulties in evaluating the performance of climate models in Africa are also due to the high natural variability of precipitation in Africa, as Benjamin Sultan points out in his article: https://theconversation.com/secheresses-en-afrique-et-rechauffement-climatique-attention-aux-raccourcis-191447
[2] https://public.wmo.int/en/resources/library/2020-state-of-climate-services-report; https://theconversation.com/secheresses-en-afrique-et-rechauffement-climatique-attention-aux-raccourcis-191447
