diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml
index a52bfad2f3d..d329388bb9a 100644
--- a/doc/src/sgml/ref/create_table.sgml
+++ b/doc/src/sgml/ref/create_table.sgml
@@ -163,7 +163,8 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXI
      <para>
       Optionally, <literal>GLOBAL</literal> or <literal>LOCAL</literal>
       can be written before <literal>TEMPORARY</> or <literal>TEMP</>.
-      This makes no difference in <productname>PostgreSQL</>, but see
+      This presently makes no difference in <productname>PostgreSQL</>
+      and is deprecated; see
       <xref linkend="sql-createtable-compatibility"
       endterm="sql-createtable-compatibility-title">.
      </para>
@@ -1304,13 +1305,20 @@ CREATE TABLE employees OF employee_type (
    </para>
 
    <para>
-    The standard's distinction between global and local temporary tables
-    is not in <productname>PostgreSQL</productname>, since that distinction
-    depends on the concept of modules, which
-    <productname>PostgreSQL</productname> does not have.
+    The SQL standard also distinguishes between global and local temporary
+    tables, where a local temporary table is only visible within a specific
+    SQL module, though its definition is still shared across sessions.  Since
+    <productname>PostgreSQL</productname> does not support SQL modules, this
+    distinction is not relevant in <productname>PostgreSQL</productname>.
+   </para>
+
+   <para>
     For compatibility's sake, <productname>PostgreSQL</productname> will
     accept the <literal>GLOBAL</literal> and <literal>LOCAL</literal> keywords
-    in a temporary table declaration, but they have no effect.
+    in a temporary table declaration, but they currently have no effect.
+    Use of these keywords is discouraged, since future versions of
+    <productname>PostgreSQL</productname> might adopt a more
+    standard-compliant interpretation of their meaning.
    </para>
 
    <para>
diff --git a/doc/src/sgml/ref/create_table_as.sgml b/doc/src/sgml/ref/create_table_as.sgml
index 1be9f4d1f6a..29d161940c7 100644
--- a/doc/src/sgml/ref/create_table_as.sgml
+++ b/doc/src/sgml/ref/create_table_as.sgml
@@ -62,9 +62,8 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE <replaceable
     <term><literal>GLOBAL</literal> or <literal>LOCAL</literal></term>
     <listitem>
      <para>
-      Ignored for compatibility. Refer to <xref
-      linkend="sql-createtable"> for
-      details.
+      Ignored for compatibility.  Use of these keywords is deprecated;
+      refer to <xref linkend="sql-createtable"> for details.
      </para>
     </listitem>
    </varlistentry>
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 9eb1bed58e6..8389337ecc2 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -2507,15 +2507,31 @@ CreateStmt:	CREATE OptTemp TABLE qualified_name '(' OptTableElementList ')'
  * Redundancy here is needed to avoid shift/reduce conflicts,
  * since TEMP is not a reserved word.  See also OptTempTableName.
  *
- * NOTE: we accept both GLOBAL and LOCAL options; since we have no modules
- * the LOCAL keyword is really meaningless.
+ * NOTE: we accept both GLOBAL and LOCAL options.  They currently do nothing,
+ * but future versions might consider GLOBAL to request SQL-spec-compliant
+ * temp table behavior, so warn about that.  Since we have no modules the
+ * LOCAL keyword is really meaningless; furthermore, some other products
+ * implement LOCAL as meaning the same as our default temp table behavior,
+ * so we'll probably continue to treat LOCAL as a noise word.
  */
 OptTemp:	TEMPORARY					{ $$ = RELPERSISTENCE_TEMP; }
 			| TEMP						{ $$ = RELPERSISTENCE_TEMP; }
 			| LOCAL TEMPORARY			{ $$ = RELPERSISTENCE_TEMP; }
 			| LOCAL TEMP				{ $$ = RELPERSISTENCE_TEMP; }
-			| GLOBAL TEMPORARY			{ $$ = RELPERSISTENCE_TEMP; }
-			| GLOBAL TEMP				{ $$ = RELPERSISTENCE_TEMP; }
+			| GLOBAL TEMPORARY
+				{
+					ereport(WARNING,
+							(errmsg("GLOBAL is deprecated in temporary table creation"),
+							 parser_errposition(@1)));
+					$$ = RELPERSISTENCE_TEMP;
+				}
+			| GLOBAL TEMP
+				{
+					ereport(WARNING,
+							(errmsg("GLOBAL is deprecated in temporary table creation"),
+							 parser_errposition(@1)));
+					$$ = RELPERSISTENCE_TEMP;
+				}
 			| UNLOGGED					{ $$ = RELPERSISTENCE_UNLOGGED; }
 			| /*EMPTY*/					{ $$ = RELPERSISTENCE_PERMANENT; }
 		;
@@ -8930,11 +8946,17 @@ OptTempTableName:
 				}
 			| GLOBAL TEMPORARY opt_table qualified_name
 				{
+					ereport(WARNING,
+							(errmsg("GLOBAL is deprecated in temporary table creation"),
+							 parser_errposition(@1)));
 					$$ = $4;
 					$$->relpersistence = RELPERSISTENCE_TEMP;
 				}
 			| GLOBAL TEMP opt_table qualified_name
 				{
+					ereport(WARNING,
+							(errmsg("GLOBAL is deprecated in temporary table creation"),
+							 parser_errposition(@1)));
 					$$ = $4;
 					$$->relpersistence = RELPERSISTENCE_TEMP;
 				}