The bicycle as a weather vehicle: transects of the urban CO2 and weather measurements on a bicycle-based atmospheric sensor

It is well known that the CO2 is one of the main greenhouse gases. The traffic of non-electric vehicles is the main contribution to the emissions of this gas in the cities, enhancing the urban heat island effect and increasing the dangers of global warming. The changes in the amount of CO2 across the city occur on a small urban scale, easily measured by a person moving around the city, whether it be walking or cycling. A handheld CO2 sensor capable of recording this gas, temperature, atmospheric pressure, and relative humidity has been mounted on a bicycle to analyse local variations of this gas in a couple of cycling route transects in Barcelona city and some of municipality in its metropolitan area. The results presented here show a local CO2 variability, with some changes of this gas in 90 ppm over distances of few hundreds of meters (less than 1 km). The influence of parks, urban forests, and gardens in absorbing the gas has also been identified. The measurements obtained with this technique demonstrate that using a bicycle as a scientific vehicle is a viable method to analyse the C02, temperature, humidity and pressure distribution in urban and periurban areas, which could be used as a scientific citizen project helping to monitoring the amount of CO2 in urban areas. Many cities and municipalities worldwide are making an effort to adapt their infrastructures by including bike lanes, with the purpose of promoting bicycles as a common mobility vehicle. Bicycles are spreading out throughout cities as a useful and efficient vehicle. Thousands of cyclists moving through urban areas is also an opportunity to use the bicycle as a scientific vehicle to measure and helping monitoring some atmospheric variables (such as temperature, relative humidity, or CO2 values), thus inciting citizens to collaborate with scientists in quantifying the evolution of this gas in urban areas.