On this, my first, contribution to the MPE2013 blog I am particularly lucky to be able to announce to you that MPE2013 received the patronage of UNESCO. This includes, in particular, the international launch of the *Mathematics of Planet Earth Open-Source Exhibition* scheduled to take place in February, 2013.

As you can see, we will have an MPE2013 blog. We expect to have occasional contributions in 2012, and we anticipate daily contributions starting January 1, 2013. This testifies to the magnitude of MPE2013.

Of course, we have not yet planned for 365 bloggers for 2013! We need your help with a contribution. What could be a contribution? It could be a personal commentary on any topic associated with MPE2013: a report on a meeting, a pointer to important research results, a website recommendation, a short essay on a key issue, a book review, a news item, or any other material that might be of interest to a broad audience. A contribution can be as short as a couple of paragraphs and may include a photo or illustration or even an audio or video clip. You may choose your date(s) and topic(s) to blog about your favorite event(s). We understand that last-minute changes are part of the action. To register, send a message to blog@mpe2013.org, with an indication of preferred dates and topics.

I intend to blog regularly in 2013. I will use the blog to share with you the new developments of MPE2013. But you will also discover that one of my passions is popularization of mathematics. I am a regular contributor to the (French) magazine **Accromath**. This magazine is preparing a special issue on Mathematics of Planet Earth for the beginning of 2013, and we hope for a wide distribution of this special issue outside the province of Quebec. If you look at the archives of Accromath, you will see that we have highlighted all the articles that are related to MPE topics. If more magazines around the world do the same, then this will allow for significant material that teachers will be able to bring to the classroom.

It is now three years that I have been working on MPE2013, and my main reward in this venture is that I always discover new mathematics hidden in some MPE topic, learn about the beautiful mathematics in others, and understand some of the mathematical challenges in the science of climate and sustainability. There are several important ingredients in good research: one is the significance of the question considered, and another is the power of the tools developed or used to solve it. These could be independent matters. Mathematicians are good problem solvers. They have powerful tools, and they are able to create new tools for new problems. But this is not sufficient. We need to ask the right questions, we need to use the right models. It could be very tempting to pass a line through a cloud of points, but what if the cloud of points is the beginning of an exponential phenomenon? Linear models can give a good fit with data on short intervals, but are we allowed to extrapolate over longer intervals? When we model a phenomenon, have we forgotten an essential parameter? Can we consider the model in isolation, or is the system influenced by other variables in a larger model? Let me share with you some of the new things I learned recently.

Daniel Pauly, from the UBC Fisheries Centre, recently gave a public lecture at Centre de Recherches Mathématiques (CRM) on the state of fisheries in the world. He talked of the decline of the cod population in the Atlantic. There were two contradictory signals: the catches by small boats close to the Eastern Canadian coast were decreasing drastically, but there was no significant decrease in the deep-sea fishing catches. Which signal to follow? The choice was made to ignore the first signal, with the result that after almost 20 years there was almost no cod left in the Atlantic. We now know that there was no contradiction between the two signals: even when there are a few cods left, they stay together over a reduced areas, thus allowing for good catches.

Last week, I learned from Robert Smith? (sic) about the successful mathematical modeling of the Guinea worm. I was five years old living in Guinea when for the first time I heard the adults explaining the risk of catching this worm, which could be a meter long and would live inside your body, usually your foot. The complicated life cycle of this worm is well known, the disease is now decreasing, and we can dream of eradicating it in the near future. Among the many parameters, the one that proved the most important is education! When one’s foot hurts, it is very tempting to put it in water. It is the moment that the worm chooses to lay 100,000 eggs. Education gives better results than chlorinating the water and the other techniques that have been tried. This example shows that we must keep an open mind when we do research on MPE topics.

As an inhabitant of the Earth and a curious person, I am always trying to better understand our planet. A year ago, not long after the earthquake in Japan, I received the following message from John McKay: “I am asking whether there will be a session on the effect of earthquakes on the rotation speed of the Earth?” and we started exchanging messages on the matter. I remarked that a change of the rotation speed of the Earth forces many adjustments: recalibrating the telescopes, since the polar axis of the Earth might have changed position, readjusting the GPS, etc. Could this phenomenon be a good topic for a module for the MPE competition? Could it be a starting point for a modeling discussion in your course? The modeling could start with the physical situation: the closer the mass to the center of the Earth, the faster the rotation. Then, how do you orient the axis of the telescope so that only one rotation movement suffices to keep the focus on a star during a long observation period? You need not solve all the problems. Asking questions is also part of the game.

Christiane Rousseau