Carmena is communist, an "elpais" is a leftist newspaper. They are partial and you can not trust them on this. Specially now that we are under elections.

An 8% difference with last year is nothing in Madrid. Madrid has big differences in pollution depending on what it rains, and specially on the wind. Pollution is bad there when there are anticyclonic weather and thermal inversion.

Madrid has very clear skies, it is like Denver,Colorado. The near mountains filter the low clouds. So at night most heat is radiated, making inversion frequent.

Carmena has created chaos in Madrid, an enormous congestion, just ask any taxi driver. I talked with people in the Politecnic University in Madrid in Winter and some levels of pollution were higher this year than last one(last year rained a lot so it was very clean).

I'd bet those numbers have been cooked to make Carmena look good. Most of the traffic goes now around the perimeter created and those places are way worse than last year.

In Spain most of the Media is controlled by the left and now also the leftist Government, that directly controls public Media(In Spain public Media depends on taxes, not like the BBC or Media in Europe).

Carmena is not a great technical person. She acts on feeling and ideology. Facts care very little to her.