Higher CO2 pollution in the North during winter

Autumn leaves. By: Linda Bergqvist

Seasonal CO2 levels in the North visible from space

I was out walking and photographing landscapes thinking how the air felt much “dirtier”, as in more polluted, and remembered that the Northern Hemisphere actually have higher CO2 values (ppm) in winter time due to loss of photosynthesis. NASA released a really good illustration of this last year shown below.

In the video we can see, for the year 2006, how plumes of CO2 shift as winds disperse gasses away from the original sources, mainly located in the Northern Hemisphere were a majority of the global population is located. We also see how CO2 levels go up and down in the Northern Hemisphere along with the growth cycle of plants and trees.

For people in the Northern Hemisphere, especially between 45 to 70 º N latitude, we can see a change in the greening of ecosystems with earlier springs and later frost. In other words, humans are not only increasing the overall CO2 levels over time but also causing seasonal changes due to global warming. The rate of temperature increase in Sweden has been double that of the global average. The change in seasonal vegetation cover is particularly visible in northern Sweden where warming has been more pronounced.
The graph shows number of days with increase in vegetation, averaged over a ten year period, in northern Sweden. From 1960s until 2014 we have observed a 14 days increase. Source: SMHI
After 1990 the first frost days in Autumn has started arriving later, on average. Days of earlier frost should be interpreted with care as the location of measuring stations may impact the results.
Differences in number of days after 1st of July when first frost of the autumn arrives. Between periods 1991-2013 and 1961-1990. Source: SMHI

Human health impacts

Except the serious ecosystem impacts these changes have, such as alterations in blooming, mating and migration patterns, what are some of the direct human health impacts? Well, according to a recent Harvard study elevated CO2 levels negatively impact human cognitive function. The study conducted controlled experiments inside office buildings, where values often are high, measuring cognitive ability under different CO2 levels (ppm) and found that, on average, participant’s cognitive scores dropped significantly with values above 500 ppm. According to the study, impacts on crisis response, information usage and strategy (which are indicators of high level cognitive function and decision-making) were all greatly reduced under high CO2 values.
Cognitive score (y-axis) and CO2 levels ppm (x-axis).

Baseline values are the same as outdoor values, i.e. around 400 ppm, and indoor values of 200-400 ppm higher than outdoors are unfortunately commonplace. As one would expect it's worse in big cities, where CO2 levels are higher. Poor ventilation can thus have major impacts on worker productivity and health. Still, we don't know the threshold at which CO2 levels begin to measurably impact human cognition. Some studies have pointed towards a threshold of 600 ppm but the safest way to proceed is simply by lowering greenhouse gas emissions, while we still are are smart enough to do so.


Out of the ashes into the fire

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