In a thermochemical equation, the change is always written next to the balanced chemical equation

In a thermochemical equation, the enthalpy change is always written next to the balanced chemical equation.

For example, chemical reaction: 2Mg + O₂ → 2MgO. ΔH = -1204 kJ; this is exothermic reaction,
or chemical reaction: Fe₂O₃(s) + 3CO(g) → 2Fe(s) + 3CO₂(g);ΔH = + 26.3 kJ, ths is endothermic reaction.
There are two types of reaction: endothermic reaction (chemical reaction that absorbs more energy than it releases) and exothermic reaction (chemical reaction that releases more energy than it absorbs). 

Needs for population

My best guess is that most of the earth would freeze causing an almost ice age like catastrophe