Urban heat island map

Urban heat island map reveals how NASA satellites track the phenomenon raising city temperatures, with global data and public health impact.

About this subject

Urban heat islands are metropolitan areas significantly warmer than surrounding rural zones due to human activities, pavement, and buildings. The phenomenon was first documented in 1818 by Luke Howard but intensified with city growth. Satellites such as Landsat and MODIS (Moderate Resolution Imaging Spectroradiometer) aboard NASA's Terra and Aqua satellites map land surface temperature at resolutions up to 30 meters, identifying hotspots. Cities use these data to plan green roofs, reflective pavements, and tree canopies, reducing temperatures by up to 2.5 °C.

In Brazil, the National Institute for Space Research (INPE) monitors the phenomenon in partnership with international agencies. São Paulo, for example, records differences of up to 10 °C between downtown and peripheral vegetated areas. The global urban heat island map, available on platforms like the Global Urban Heat Island Explorer, combines remote sensing with climate models to predict heat waves. The European Space Agency (ESA) contributes with Sentinel-3 satellite, which measures land surface temperature at 1 km resolution.

Consequences of heat islands go beyond thermal discomfort. They increase electricity demand, worsen air pollution (tropospheric ozone formation), and raise mortality risk during heat waves. IPCC studies indicate that if cities do not adopt mitigation measures, maximum temperatures could rise by 3 °C to 5 °C by 2050. Initiatives like the UN Cool Cities Network encourage the use of satellite data for sustainable urban planning, integrating citizen science and continuous monitoring.

Frequently Asked Questions

What causes urban heat islands?

The replacement of natural surfaces with asphalt, concrete, and dark roofs that absorb and retain heat, along with reduced vegetation and heat from vehicles and machinery.

How do satellites measure urban heat islands?

Thermal infrared sensors such as MODIS and Landsat TIRS detect radiation emitted by surfaces, converting it to temperature with spatial resolutions from 30 to 1000 meters.

Which Brazilian cities are most affected by heat islands?

São Paulo, Rio de Janeiro, Belo Horizonte and Brasília, where the difference between urban core and green areas can exceed 8 °C.