Query: The 2nd law of thermodynamics is consistent with the greenhouse effect which is directly observed.

Relevant passages:
Water vapor <=SEP=> Water vapor , water vapour or aqueous vapor is the gaseous phase of water . It is one state of water within the hydrosphere . Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice . Unlike other forms of water , water vapor is invisible . Under typical atmospheric conditions , water vapor is continuously generated by evaporation and removed by condensation . It is lighter than air and triggers convection currents that can lead to clouds .   Being a component of Earth 's hydrosphere and hydrologic cycle , it is particularly abundant in Earth 's atmosphere where it is also a potent greenhouse gas along with other gases such as carbon dioxide and methane . Use of water vapor , as steam , has been important to humans for cooking and as a major component in energy production and transport systems since the industrial revolution .   Water vapor is a relatively common atmospheric constituent , present even in the solar atmosphere as well as every planet in the Solar System and many astronomical objects including natural satellites , comets and even large asteroids . Likewise the detection of extrasolar water vapor would indicate a similar distribution in other planetary systems . Water vapor is significant in that it can be indirect evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects .

Second law of thermodynamics <=SEP=> The second law of thermodynamics states that the total entropy of an isolated system can only increase over time . It can remain constant in ideal cases where the system is in a steady state ( equilibrium ) or undergoing a reversible process . The increase in entropy accounts for the irreversibility of natural processes , and the asymmetry between future and past .   Historically , the second law was an empirical finding that was accepted as an axiom of thermodynamic theory . Statistical thermodynamics , classical or quantum , explains the microscopic origin of the law .   The second law has been expressed in many ways . Its first formulation is credited to the French scientist Sadi Carnot in 1824 , who showed that there is an upper limit to the efficiency of conversion of heat to work in a heat engine .

Thermodynamics <=SEP=> Thermodynamics is a branch of physics concerned with heat and temperature and their relation to energy and work . The behavior of these quantities is governed by the four laws of thermodynamics , irrespective of the composition or specific properties of the material or system in question . The laws of thermodynamics are explained in terms of microscopic constituents by statistical mechanics . Thermodynamics applies to a wide variety of topics in science and engineering , especially physical chemistry , chemical engineering and mechanical engineering .   Historically , thermodynamics developed out of a desire to increase the efficiency of early steam engines , particularly through the work of French physicist Nicolas Léonard Sadi Carnot ( 1824 ) who believed that engine efficiency was the key that could help France win the Napoleonic Wars . Scottish physicist Lord Kelvin was the first to formulate a concise definition of thermodynamics in 1854 which stated , `` Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies , and the relation of heat to electrical agency . ''   The initial application of thermodynamics to mechanical heat engines was extended early on to the study of chemical compounds and chemical reactions . Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field . Other formulations of thermodynamics emerged in the following decades . Statistical thermodynamics , or statistical mechanics , concerned itself with statistical predictions of the collective motion of particles from their microscopic behavior . In 1909 , Constantin Carathéodory presented a purely mathematical approach to the field in his axiomatic formulation of thermodynamics , a description often referred to as geometrical thermodynamics .