Results yes, limitations

2009/06/01 Lakar Iraizoz, Oihane - Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Ingurumena
• Klima
• Fisika

A basic principle of physics is the conservation of energy.

Evonne McArthur

Energy from the Sun, atmosphere, oceans and Earth, among which are complex interactions that result in a local climate. Logically, behind these interactions are the basic principles of physics: "Mass is preserved, also energy; according to Newton's laws, air moves from side to side, etc. explains the physicist of the UPV Climate, Meteorology and Environment Group, Jon Saenz. "Based on these principles of physics, climate models simulate the world climate," he says.

These basic principles are expressed through complex equations and resolved in supercomputers. Without a supercomputer it would be impossible to analyze the world climate system because, on the one hand, they have to solve a lot of terrible operations and, on the other, they have to simulate the world climate.

The substitution of all climate interactions and factors in models is impossible. One of these limitations is the very power of computers, "there are no computers with enough power in the world," says Saenz. Another is the degree of understanding of scientists, since they do not correctly understand all the processes that affect the climate, since it is an extremely complex system. Scientists are building models as they understand the functioning of the climate. Proof of this is that they introduce increasingly complex equations in computers to simulate the world climate.

Saenz told us, however, that the intention of the models is not at all to completely replace the climate: "the system is complex and equations simplify the system to a greater or lesser extent." In addition, they simulate climate around the world and must simulate the world in their models. How is it done? Saenz explains: "You have to tell the computer at what point in the world you must solve the equations. For this we draw in the world an imaginary network that is divided into cells. In these cells we agree at what point we will solve the equations and consider that the values in the point-to-point range will be similar. The cells of the models currently used have an approximate distance of 100 kilometers. Discretization is the representation of the world through certain points. Of course, by doing that we always lose the information."

On the other hand, all models are based on the basic principles of physics, but when defining the expressive equations of these principles, they must simplify reality. Saenz explained this by an example: "Take, for example, moisture. In fact, when the relative humidity is 100%, it should rain. But we know that reality is more complex and that the humidity to rain does not have to be 100%. In models, however, it is necessary to simplify reality and fix in a specific humidity when it rains. For this we are testing. We define a series of humidity and see that the simulation of the model causes moisture to correspond to what happened in reality."

The study of ice accumulated at the poles allows researchers to know the atmospheric composition of past times.

DAP

Like humidity, they incorporate hundreds of other parameters in the models. "However, not everyone who works with models uses the same parameters and does not solve the equations in the same way," said Saenz. "Therefore, not all models give the same results. Depending on the model used, one result or another is obtained," he adds.

Despite all these limitations, Saenz has told us that they represent quite reliably the weather conditions of the past: "We have data collected in a lot of years and match situations that represent real data and simulate models. "The results are not very different, most are in a certain range of variability. It is logical to think, and that is what is seen in most cases, that the real value is within that interval." For example, the Intergovernmental Panel on Climate Change (IPCC) uses simulations of 10-23 climate models to prepare its reports.

Instruments to predict the future

If they fairly reliably simulate the weather conditions of the past, it is to be assumed that they can also serve to predict the climate of the future. For this it is necessary to know the future conditions. And the truth is that it is impossible to know.

However, the objective of climate models is to somehow predict what climate will be in the future, taking certain possible conditions. The IPCC has established these possible conditions and proposed possible situations. The IPCC itself explains on its website the evolution of the population, economic development, energy demand, the use of energy, the availability of resources, technological changes, changes in land use and environmental policies.

Jon Saenz Aguirre. Doctor of Physics, professor of Meteorology and Climatology at UPV/EHU and director of the Climate, Meteorology and Environment Group. In recent years great advances are being made in climate simulation models.

Recent searches

They will define, according to the IPCC, human influence on climate in the future. "Then," Saenzek-says, "those who work with models incorporate in the models the conditions proposed for each situation and analyze the changes that could cause."

"These are not predictions but projections," Saenz explains. "Saying is making an ad is going to happen so much. The projections say that if these conditions existed, this and this would happen."

And there is, according to Saenz, the greatest uncertainty about the future climate: "The greatest uncertainty is not in mathematics, I think the greatest uncertainty lies in the situations proposed by the IPCC. It is impossible to predict how many people we will be within a hundred years, how much energy we consume, where we get from, etc. Who would say that 30 years ago the Internet would exist?"

However, all models suggest an increase in global temperature. So says Saenz: "What I can say is that the temperature does not drop. We cannot make an estimate, but we can say that the future will be warmer. And in this situation we must be cautious."

Skeptics at the end of uncertainty

Reliability and limits of climate models: rainfall today and in the future. The distribution of rainfall is represented in the left column, between December and February, and in the right between June and August. The data observed in the upper line appear represented, in the central, how the models have simulated what happened and in the lower, the projection of different models for the period 2090-2099. The blank spaces indicate that the results of the models do not match for these fields.

SOURCE: IPCC 2007: WG1-AR4.

It cannot be said that the issue is not complex, there are uncertainties everywhere. This allows interpretations in multiple ways. And, of course, there are those who take uncertainty to the extreme and question climate change itself. All kinds of arguments can be heard by skeptics. For example, Nils-Axel M rner, a retired geophysicist from Sweden, claims that sea level does not rise. He acknowledges that there are areas where sea level is rising, such as Venice or Hong Kong, but he believes the reason is that these places are sinking.

One of the most well-known sceptics of Euskal Herria is Ant n Uriarte. Uriarte focuses mainly on carbon dioxide. "The increase in carbon dioxide levels is beneficial because this improves plant photosynthesis, and there is nothing more to see than in the past, when the concentration of carbon dioxide was much higher than the current one, vegetation was abundant," says Uriarte.

Knowing how to address skeptics is not easy. The fact that someone who is not an expert on climate issues starts doing so is crazy: based on the same data, some do a reading and others do the opposite.

How to know, then, who is right? What is the truth? The most direct way would be to go to specialized magazines. In fact, in specialized journals, to decide whether or not to publish articles, that is, to know whether their arguments and data to protect them are reliable enough, they turn to and analyze other experts. It is the most objective form of screening.

If it is sought following this criterion, it can be observed that the arguments of skeptics appear very rarely published in specialized scientific journals. Naomi Oresi, a professor of history and scientific research at the University of California, analyzed articles published in scientific journals between 1993 and 2003. The conclusion was that no one bet on skeptics.

Climate models simulate meteorological phenomena. In this image, for example, clouds and precipitation have been simulated in a specific area at the Japanese Agency for Science Technology of the Sea and Earth.

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Oreskes did not find any articles of skeptics, but Clausura Martin Schutle, an endocrinological surgeon at King's College Hospital, analyzed the articles published between 2004 and 2007. Schutl concluded that 6% of the articles were against the official position.

When we talk about an official attitude, we are talking about an attitude that supports the IPCC, that the world is warming and will continue on that path. Someone might think that those who make reports are under heavy pressure from politicians, companies, etc. and that they somehow feel compelled to adhere to the official position. Saenz has not noticed, however: "The scientists who support the final IPCC report are not of any kind, they are already prestigious scientists and I think they won nothing for this work. That's why I think they're pretty objective."

Speed of change

Serve these lines to define a little the information that citizens receive through the media, non-profit, yes, to have a precise knowledge of what can happen. The climate has always had and will have fluctuations, as our planet receives energy from an external source of irregular and changing shape. In addition, we know that the concentration of greenhouse gases has also undergone variations in the past and continues to evolve by natural causes.

Adolfo Uriarte. Oceanographer, Market Director of the Marine Research Unit of AZTI-Tecnalia.

However, it is also true that human activity is changing the levels of some greenhouse gases (mainly CO 2), at a rate unknown to those who have so far investigated past variations of gases. If we continue with the current rate of growth, as the end of the century we will double the atmospheric concentration of CO 2. Therefore, the problem is not to increase concentration, but the speed of change. What we must know is whether terrestrial and marine organisms and systems will be able to cope with this rapid change by adapting their functioning to the new conditions and putting in place the processes necessary to recover the balance of the system. It seems that it will be difficult.

Finally, I would like to highlight the need for solidarity with the following generations. Changes already introduced in the system present inertia of unknown size. Although we stopped issuing CO 2, these inertia could induce changes, whose dimensions and scope are unknown. The least we could ask for is prudence and solidarity.

Responsibility is our responsibility

(Source: IPCC 2007: WG1-AR4.)

In the latest IPCC report, these graphs protect, among other things, that current warming is occurring by human action. XIX. In the 20th century, fluctuations in global mean temperature are shown, representing variations measured by the black line and temperature variations simulated by yellow and blue marks (specifically, 58 simulations made by 14 models). With the realization of the yellow lines, natural factors that influence the climate and depend on humans were introduced into climate models. The blue lines, however, took into account only natural factors, leaving aside human influence on the climate. In both expressions the uncertainty of the models is the same and, however, it is quite clear that simulations that take into account human influence better reflect the observed incidence.

Climate change: What to do?

Climate change is an undeniable social fact from the point of view of scientific consensus, regardless of the existing uncertainties: the increase in global temperature and its physical consequences. On the contrary, it is more slippery to clearly define the social consequences of climate change.

We are trying to imagine a society of the future -- at 50-100 years, or even later -- so that the predictable catastrophic future does not become reality if we do nothing. That is to say, to project the current trends towards the future (forecasting), we are moving to a backward projection, marking from the future the objectives for the present (backcasting) with the aim of “controlling” that future. Never before had such a thing been done, so consciously, in world society.

Mercedes Pardo. Professor of Sociology of Climate Change, Universidad Carlos III de Madrid.

So what to do? although the question is not very concrete, it is more necessary than ever. It is true that we are already doing many things, but there is still little left to do, taking into account the dimension of the problem. A world with 2 C of temperature rise, 4 C more, may be a very different world, without a doubt. So it's good to ask what else do we do? ".

It is about making a great social transformation in our way of producing, in our way of consuming, in our way of eating, in our way of transport, in our way of building, in our way of relating to the rest of the world and, ultimately, in our way of life. And all this in the short term. The challenge is huge and so it is important what to do? Question.