One of the world's greatest threats in the 21st century is not just to the environment. Climate change has increased dramatically in recent decades, with significant and prolonged global variations. 

The effects themselves are quite local, translating into extreme events of cold and heat, which unbalance ecosystems and even threaten the survival of the human species in certain regions. All of this is interconnected with the thawing of the poles, the rise in sea level and the acidification of water caused by the increase in carbon dioxide (CO2) emissions. It is time to act, now or never.

The BBC recently compiled a list of black spots in climate change, supported in detail by scientific and graphic data, with very pessimistic predictions about the future if we opt for inaction. And by exceeding the parameters outlined in an exhaustive list by the European Commission on consequences that are already being felt, we have come to four major challenges.

1. Planet clearly warming up

Planet Earth is getting warmer from day to day. It is not a matter of feeling or belief, it is a fact. According to the UN World Meteorological Organization, the world's average temperature is 1ºC above what was in the industrial era, late 19th century.

The North American NOAA (Oceanic and National Atmospheric Administration) indicates that 2019 was the second warmest year since records have been kept (1880), surpassed only by 2016. Almost 400 maximum temperature records were broken in the summer of 2019 alone, just in the Northern Hemisphere, most of them in European countries.

2. Cities under notice

All countries in the world will be affected by climate change, whether through cold or heat, with greater or lesser intensity. Cities, due to their high population concentration and location, are at the forefront, facing more storms, hurricanes, or droughts, not to mention the increase in sea water levels.

The world's population is increasingly urban, with 50% now living in cities, and it is estimated that this percentage will reach 70% in the next 50 years. The challenges are enormous, because even at the current level, cities and urban areas already account for 75% of CO2 emissions. It is necessary to reinvent cities and change how they function, whether in terms transportation, the use of water or sanitation, without forgetting the adaptation to the adverse effects of the climate.

3. Oceans at risk

The effect of high temperature and thaw on the oceans does not manifest solely in an increase in water levels. It is an entire ecosystem, or several, threatened by the increased absorption of CO2, which makes the oceans warmer and more acidic,deeply affecting marine currents, affecting all aquatic life, coastal areas and the interior of the continents. It is enough to consider that animals and plants have taken thousands and thousands of years to adapt to specific living conditions - hence all the diversity that our planet sustains - so, for many species, two or three centuries make it virtually impossible to adapt.  

The next step is to reverse the current trend, drastically reducing pollutant emissions, thus preventing them from spreading through the atmosphere and unbalancing the oceans. This, according to BBC data, aims to halt the increase in the average temperature at 1.5 ° C. It sounds small, but it can make all the difference. It sounds easy, but it's a Herculean task.

4. Opposites attract more and more

The extreme cold and heat phenomena have caused catastrophes worldwide, and this tendency, unfortunately, will grow. According to a 2018 report by the IPCC (International Panel on Climate Change), a 0.5º difference in temperature rise is sufficient to trigger the likelihood of catastrophic events.

Floods, droughts and fires will be more intense and frequent, and affect more and more people. We must learn to live in conditions that are still unknown to us, adapt our ways of life, and strengthen the resilience of our infrastructure, in cities and in the economy generally.