"since 2010 we consumed  1.5 times the production of the planet"

Eugenia Kalnay is a Distinguished University Professor at the University of Maryland (UMD) in the United States, and a member of the Scientific Advisory Board at United Nations

She was Branch Head at NASA Goddard, and later served for 10 years as the Director of the Environmental Modelling Center within the National Weather Service, where she was instrumental in major improvements in the NWS models' forecasting skill. In 2009, she received the prestigious World Meteorological Organization IMO Prize. Her work on the impact of land use on climate change was chosen by Discovery Magazine as one of the top 100 science results of 2010, and her seminal paper on reanalysis is the most cited paper in all geosciences.

#WeAreClimate talked to her to help you better understand how climate change is affecting us. This is what she said:

What percent of climate change can be associated with human behavior?

- Extreme weather events, like a record snow storm or heat wave, can be produced by either natural variability or by the accumulated impact of the humans (as shown in the graphic) so that they cannot be attributed completely to humans.

So, individual record-breaking weather events may be due about half to humans and the other half to natural variability.  But the large trends of global averages (like those shown in the Figure N° 1 and Figure N° 2 below), which shows the global mean temperature since 1880, can only be attributed to the human impact because they are much faster than any climate change previously seen. So, for climate change in large scales, I would say that essentially 100% is due to humans.

Figure 1

Figure 1

Does human factor must be considered, at this stage, inside weather models calculations?

"Not in weather models, because the limit for weather predictions is about 2 weeks, and the human impact has longer time scales. 

So the human impact (such as the increase of greenhouse gases produced by human use of fossil fuels) should be included in weather models but it is not necessary to include the human system (i.e., to couple a full model of the human factors with the atmosphere, ocean and land models).

Figure 2

Figure 2

By contrast, in climate change models like the ones used in the IPCC, and models predicting long term changes (a decade or longer), it is essential to include a human model that interacts with the Earth System model, including the two-way feedbacks that take place in reality.

For example, the figure N° 2 above, shows that over the last 10,000 years, the major greenhouse gases (CO2, methane and nitrous oxide) have increased proportionally to the human population, which clearly shows that the population is the driver of their increased emissions.

This is particularly true after 1950, when the introduction of the Haber-Bosch nitrogen fertilization started the industrial agriculture, including major increases in the use of fossil fuels for not just fertilization, but also, in pesticides, irrigation, and mechanization (this is called the Green Revolution).

From 1950 to 1984, the production of grains increased by 250%, and the population doubled. Currently the IPCC models used to predict climate change do not have feedbacks to and from the population, which is obtained from projections made by the UN (i.,e., tables without feedbacks). This necessarily leads to erroneous results."


Which is the outlook you imagine in case that CO2 emissions stay at the current rate?

- An important part of the problem should come especially from big corporations (very far nowadays). But beyond that, do you believe that a change of habits related to how every citizen consume would help to mitigate this threat?

- This is a very good question! In our paper Human And Nature DYnamical model (HANDY model), we showed with a simple mathematical model that societal collapses (that have taken place hundreds of times since agriculture started about 10,000 years ago), are due to two independent causes: 1) excessive per capita consumption of nature; and 2) Inequality between the rich and the poor.

Since the big corporations are a major contributor to inequality, both within countries and between countries, they certainly contribute in a major way to the huge growth of the total consumption of the natural resources, which can be estimated as the product of the total population and the average GDP/per capita (see Fig. 3 below).



You can see that the population and the GDP/capita, since 1950 -when industrial agriculture started, greatly increasing the consumption of fossil fuels and the greenhouse gases- have been growing at 2% each, with a total growth of about 4%. This means that the total consumption of natural resources is doubling every 20 years or so, which is completely unsustainable (since in 2010 we were already consuming ~1.5 times the production of the whole planet).  

descarga eugenia.jpg

Unfortunately, the graphic shows very clearly that we are in a very unsustainable state of consumption growth that will inevitably lead to a collapse. It is impossible to predict when the collapse(s) will take place, but it would seem that it will last less than a full century (4 generations).  

The impact of excessive consumption of natural resources at a rate much faster than what would be sustainable, is even more important than the impact of climate change itself. As Univerity of Maryland points out: "It is more than just climate change".


- From the scientific perspective, what optimistic message can you give to the society? 

- A society that is very unequal, and is consuming much more than Nature can sustain, can still survive and live well if there are policies that deal with the causes of the societal collapse, such as inequality and excessive total consumption.

This change requires policies to:

1) Reduce birth rates, so that the total population is reduced, especially in poorer countries. This is not impossible: Mexico, for example, reduced the number of births per woman from ~7 to 2.1,  between 1970 and 2006, and Brazil from more than 6 to about 1.7, about the same as China. These reductions were obtained without coercive measures, but with education and access to birth control. It has been found that, by far, the best results for birth control are obtained through the education of women.

2) Reduce inequality from the current levels (CEO's currently make well over 100 times their average employee), to something more like a factor of 10.

3) Reduce the consumption per capita. An example of how this can be achieved is Germany, who found that the 2008 economic crisis increased their unemployment substantially. The government decided to reduce unemployment by allowing people to work only 4 days a week, so that there were more jobs available to be shared by all. The cost of this reduction in work per capita was shared: the employees, the companies, and the government payed 1/3 each. Having 3-day weekends was just a bonus for the people!

Another example of a government policy that can lead to sustainability is the province of Misiones, in Argentina. The image shows the Vegetation Index measured by satellite for eastern South America. Misiones, whose government protects the forest, has the maximum detected vegetation (shown in deep red) compared to the more yellow values observed in Paraguay, Brazil, and the neighboring province of Corrientes, Argentina. The forest is the main source of income for Misiones, but they completely protect 30%, and the rest can only be used in a sustainable way.

HanDY model is also co-authored by Jorge Rivas and Safa Motesharrei.